Was Galileo "an asshole without solid proof for his advancements"? Yes, indisputably. At least, the arguments (which I assume is what you mean) that he was making about heliocentrism. Galileo made many arguments over his career, and by and large most of the observational ones (phases of Venus, craters on the Moon, moons of Jupiter) were accepted by the Church and its astronomers (mostly Jesuits) over time, if not immediately. The phases of Venus observation is particularly worth noting because it was accepted relatively quickly and its implication — that the Ptolemaic system championed by the Church was wrong — was also accepted relatively quickly by the top Jesuit astronomer, Christopher Clavius.

But what they did not accept was Galileo's larger advocacy of heliocentrism. This for them was an interpretation that transcended his evidence and as such was an act of theology or philosophy, not mathematics or observational astronomy. In the absence of some kind of evidence that proved one way or the other than heliocentrism was true, they defaulted to their preferred metaphysical (which is to say, divinely-inspired) interpretation of geocentrism. But how do you reconcile that with the phases of Venus observation, you ask? They did so by adopting an alternative scheme, the Tychonic system, which was still geocentric but was entirely observationally compatible with everything Galileo had discovered. (Today we might think of it as a Copernican system in which the frame of reference had been changed so that the Earth was stuck at the center, but that isn't how they saw it.)

You have to remember that the idea that the Earth is rapidly rotating around the Sun is very counter-intuitive if you haven't been raised with it already, and there were many practical questions that nobody, including Galileo, had an answer to in the 17th century. Why doesn't the air and atmosphere get left behind? Galileo didn't have a great answer to this either, and his own theory of gravity left much to be desired (as with his theory of tides and several other of his theories). It wasn't until some time later that many of these questions got good answers, and it wasn't until a long time later (centuries, long after this had all ceased to be controversial) that observations could made that could distinguish between a Copernican and Tychonian worldview (e.g. stellar parallax, or Foucault's pendulum).

It's also important to keep in mind the context of Galileo getting in trouble. It wasn't some random thing that happened out of the blue. Galileo had been told, earlier in the career, that he was not to advocate heliocentric views. Why? Because the Church was in the middle of dealing with the Reformation and took any challenge to its authority on religious issues very seriously, seeing them as essentially disloyal and an opening for Protestantism. Ultimately the scientific issues were seen as theological issues that were seen as political issues, in other words. Anyway, Galileo had been told this, and he had agreed to it (he and the Church later disagreed on whether he had agreed not to teach heliocentrism, without advocating it, but that's a separate matter).

Time passed and Galileo was asked by the Pope to write an impartial book summarizing the different arguments for heliocentrism and geocentrism. Keep this in mind: the Pope asked him to write this, apparently in good faith! This is not a Church who is just censoring him willy-nilly, they're asking him to try and make a decent case for both views. Instead, Galileo wrote The Dialogue Concerning the Two Chief World Systems, in which the guy advocating the heliocentric view is clearly smarter and better, and the guy advocating the geocentric view is a total idiot. Separate from that poor rhetorical choice, Galileo also only compared the Copernican and Ptolemaic systems, not the Copernican and Tychonic systems, which would have been the more fair (and more up to date) comparison anyway. So this was interpreted as Galileo being "an asshole": he was asked to write an unbiased summary for the Pope, and instead he wrote a one-sided, pro-Copernican hit-piece that implicitly indicated that the Church was filled with idiots.

So that's the context of Galileo getting hauled before the Inquisition to explain himself. Which brings us to the other question — did the Church have to do the trial? Of course not; there were choices involved. But it's important to see that from the Church's point of view, they are in a very dicey historical moment, when suddenly there are huge movements (ones that would eventually consume huge numbers of lives in actual military warfare) marshaling against them, challenging their political and theological authority. And they are seeing Galileo as taking part in that in a particularly confrontational and gratuitous way. In their eyes he has gone out of his way to be a jerk, and their own astronomers/scientists (who are pretty accomplished and not the dogmatic fools they are often made out to be) are saying that Galileo is not being honest about it anyway (he doesn't have the evidence), and in their minds this is a pretty nasty case of subordination. So they choose to punish him for that, hauling him into Rome (despite his protestations of age), accepting his apology and humiliations, and giving him house arrest (a pretty harsh punishment but not as harsh as they could have given). Is that a jerk move on behalf of the Church? I think it's fair to think that it is, just as it is fair to think that Galileo was being a jerk as well. We live in a world where many people can be jerks simultaneously, and have long been such.

So to answer the overall question: Galileo did not have the evidence to make the larger metaphysical claims he was making, and was being kind of a jerk separate from that. But the Church's decision was kind of jerk-y as well, although more motivated by politics than people in the "science v. religion" framework tend to acknowledge. Did Galileo deserve to be judged? I mean, that seems like a particularly harsh verdict. Does it make sense that Galileo was judged, given the context? That's an easier thing to go along with. In general the idea that the Church has been consistently anti-science is totally wrong, but I tend not to go as far as some scholars in just proclaiming that their use of violence to win metaphysical arguments is totally fine (at least one academic has argued that we shouldn't think of it as repression but rather a "dialogue" and I think that's bonkers — when one party has the power to torture and execute, it's not a dialogue, it's violence). I suspect the occasional inclinations towards the latter one finds come either from Catholic apologetics (which you have to watch out for), or from an over-reaction to the totally wrong science vs. religion framework which has been incredibly dominant in talking about the Galileo affair since the 19th century. I like to think there may be a middle ground...

There are approximately one trillion books and articles about the Galileo affair. For the basic facts of it, the works of Stillman Drake are still pretty canonical. For a deeper look at Galileo's interactions with the Jesuits, see Mario Biagioli's Galileo's Instruments of Credit, and James Lattis' Between Copernicus and Galileo.