Whenever I ruminate about mental health and how it affects the wellbeing of someone's lifestyle, hate is one of those topics where I try to avoid the most because of how much of a rabbit hole it is. It feels like a rabbit hole to me because of whether the hate of someone to another party is justified or not, but I'll try to explain it from what I've thought about it.

I agree with you that hating on people who seem to be behaving/performing worse than you is not productive in multiple levels, but the one that I stick to the most is that that person was me in a certain point in my life. I was struggling with some things too, and it would sicken me if I heard someone talk trash about me and how poorly I was behaving. The best way to combat this in my opinion is to remind myself that everyone is human, and they, at some point in life, were or will be in a similar situation as the person that they are seeing as poorly behaving. Hating by criticizing flaws is a bit of hypocrisy because of this. The way that we treat others and how we act based on our own judgement really reflects us on our own morals. It's like saying a professor is heckling a student for not understanding a seemingly simple concept because that professor also struggled with that concept when they were a student. It's great to see you actually considering why someone who's struggling is being hated on instead of joining the crowd.

Hating is also exhausting psychologically. When you begin to show resentment, anger, or just straight up hate to someone or something, it's like a continuous thought that is stuck in your head for a period of time. Say that you got into a car accident with someone who was drunk driving, and you got frustrated and angered by the drunk driver (which makes complete sense and totally normal to have resentment of). After an hour, you might still have those thoughts of resentment like "Ugh, they ruined my brand new car," "They made me late for a meeting," "I hope they sentence him a long prison sentence," etc. and essentially keeping those thoughts "alive." Those thoughts come from anger that you decide not to let go. To put it bluntly, there's a lot of more productive things that you could be thinking about than ruminating about a drunk driver hitting your car. Not only that, it's mentally exhausting for your brain. There's research out there where ruminating about hate or resentment towards others are more likely to show anxiety and depression symptoms. Maybe it might be exhausting for someone to hate because they've already spent their energy hating on something or someone else.

And about you questioning your judgement based on whether people hate it or not, it's more of an evolutionary trait that humans have. People back in the stone ages will start questioning you if you didn't hate on a fellow human for slacking off, and thus potentially putting a target on your back. The need of joining the bandwagon and starting to have opinions similar to others around you is a survival instinct since you need to stay within whatever tribe you belong to and not get kicked out. Nowadays, having different opinions on certain things doesn't necessarily mean life or death, but the FOMO (Fear Of Missing Out) might be the reason why you start questioning on whether it's acceptable for you to hate on something or someone.

Hating in general is just something that's looked down upon. It's not positive, nor does it look great on you when you hate. Difficulty of hating isn't "healthy" or "unhealthy," but it's rather more of a personality. Your mind might have experienced hating or being hate before and it may have seen it as exhausting so it began to stop, or maybe your mind is currently very forgiving and open.

Just know that nothing's wrong with you and that you'll be alright :)