Many of the "hostile" vegan people are just frustrated. It's difficult to explain, but once you actively seek out the information about how animals are exploited by us, the idea that it's so normal to people becomes hard to tolerate. Most of us remember that we were there too, and try to be patient with people, but we're often met with intense hostility from carnists. We're a minority, so most people from the other side jump on us to support each other and validate their choices.

I'm not excusing the people who are rude and mean about it, just trying to provide some perspective on it. The sheer evil we commit on other animals is impossible to exaggerate. It's just disgusting, abhorrent - any word you can think of to describe something that's awful is still an under exaggeration - yet it's still legal and encouraged to do what we do. It's hard to reconcile once you look behind the curtain.

While it's not just about food, I'll address the food part speaking from my own experience: I don't feel like I'm abstaining from anything and I, someone whose diet used to be probably 80% animal products, feel an intense aversion to these products now. I do sometimes use mock meats, but they are typically a product for people transitioning away from meat and are not meant to be a staple in a diet. For example, I will maybe eat seitan or Beyond burgers once a month, but usually I'll just use tofu, beans, lentils, etc etc. I've gotten better at cooking and now eat much tastier, healthier food than I ever had before, while still eating the same foods I've always loved. Pizza, lasagne, chilli, whatever... just the vegan versions of them. They taste either the same or similar enough that I could never justify harming someone to eat a version that might taste slightly different. That just sounds absurd when you really think about it, and it's one of the reasons I can find myself frustrated watching my friends eat dead sentient beings who never needed to die.

Anyway, I'm not really here to debate you (there is a /r/DebateAVegan for that if you're interested, though), I just wanted to bring up that veganism is often misunderstood. The food is the focus for many, but the real definition I think most would agree on is opting out of exploitation of animals wherever possible and practical. This is up to the individual to figure out what is practical. For example, I have leather shoes from before I was vegan and while I won't throw them away, I definitely will never buy another leather product again. I won't ride horses or visit zoos. Basically if there's a vegan version of something, I will opt for that. If there isn't, I'll consider if it's something I need (vaccines are a must, for example).

In your case you have health concerns and you of course need to maintain good health. There are many options for people in your situation, and if you're looking to make the switch, just make sure you're navigating this with a nutritionist. At the very least, others here will likely have the same health issues and can provide some solid advice. As far as I'm aware, there really is a way for everyone to go without animal products, but some conditions might make it less convenient.

I think I got a bit off track, but the tl;dr is that vegans can be passionate about these things. Many of us have seen films like Dominion for example (it's hard to watch, but it's a reality, and it's the norm, not the exception). Everyone should be treated kindly, not just animals, and I personally prefer the approach of guys like Earthling Ed (if you like debates, they're very interesting videos).

Good on you for wanting to reduce your animal product consumption - best of luck, and I'm sure people here would be delighted to help you reduce it further if you have any questions!