I don't hate vegans. I even dated one for a while. She would eat veggies, I would eat meat. It worked because neither of us were dismissive of the others choice.
I do hate being preached to. I think most people do. Many of my encounters with vegans were ones where they were very hostile to me. For just not being vegan. I wasn't going around telling them veganism was bad or that they were a terrible person for being vegan. I have been told that by vegans. That I am a bad person for eating meat.
I have to eat meat I have always had a high metabolism. At various times in my life my maintenance diet had to be at least 3,000 calories. Plus of course any additional food needed for non maintenance activities. Additionally I'm allergic to soy. This means that it would be nearly impossible for me to have gotten enough food without eating meat. I am pretty certain that if I had not eaten meat and animal fat. I would have died as a child, or at best had serious issues with nutrition. I was well fed as a child. I could eat as much as I wanted, still many of my memories of childhood were ones of hunger.
I even explained this to someone once and they responded by saying "well you didn't die" and then heavily implied they wish I did. As if me not dying made my point invalid.
This is why I am skeptical of vegans and vegan ideology. It is often toxic, and actively tries to hurt and shame people. Even people like me who are effectively choiceless in regards to eating meat.
Often even non-militant vegans will allow this behavior. I know how frustrating it can be to be told you need to police your own community. Though that doesn't mean it's okay to allow bad behavior amongst your peers.