Because the Internet makes it easy to more forcefully express strong opinions, from both parties.

It's very easy to run into vegans on the Internet who will call you an unethical monster for eating meat, which if you don't think of yourself as an unethical monster, can be a bit offensive.

You also run into non-vegans who can't get it through their heads that that's not every vegan on earth, or even just the Internet or likely even that conversation.

It's much harder to call someone an animal hating monster or a pretentious condescending asshole face to face.

I respect other people's choices in what to consume, and I expect the same respect in return. I have no problem with people being vegan or vegetarian. In fact, most people I work with are from India and are vegetarian. We eat lunch together most days and no one has any problems with each other.

Unfortunately most vegans I know are extremely pushy and judgemental about their diet/lifestyle. They do not respect my choice in what to consume. This used to causes some preemptive judgements on my part, where I would get defensive immediately about my dietary choices, because I assumed they were judging me. Over time I have learned to control this reflex.

I can only assume that many people have had the same experience as me, and jump to the same conclusions.

Some people feel judged for eating meat if they learn that you're a vegetarian or vegan. As veganism appears more extreme, it causes a stronger reaction.
These people don't like being judged, so they seek to judge you instead. If they can judge you for not eating meat, you can't judge them for eating it, or so they feel.
Some vegans being quite obnoxious in their attempts to convert others, doesn't improve things. Rather, it helps those who dislike vegans to reaffirm their beliefs that all vegans are silently judging them all the time.
All of this is just my theory.

There are some very militant vegans out here on Lemmy, equating eating meat with rape and murder and generally being annoying without actually contributing to the discussions.

They are actively harming their cause. So much so, I suspect them of actually being trolls trying to make vegans look bad.

Or they are just dumb as a brick and don't understand common discourse. That's possible too.

Some ideas on the topic.

I've only met vegans on social media. The vocal minority preaching vegan lifestyle is delusional. Outside of it, it's still corporations doing their best to make a profit. The regular person just eats quietly and lives their life. The requirements and costs are pittance only in their idealistic view of the world. "If only people would just .." No. They won't. We are where we are because people don't. Everyone wants the world to go their way and we kill each other for it.

As an omnivore animal, I eat what my budget allows. Sometimes it's meat, sometimes it's vegetables and sometimes it's cardboard. Just like the wild life, eating plastic bags because they taste yummy. Social media vegans seem to be either the ones that can afford to be picky or can't afford anything else.

Simple truth is that life can always be better, people can always do more and most of us simply don't want to.

I think a lot of people also have a hard time seeing it as a priority for themselves compared to their personal problems and other ongoings. It's subjective, sure. But it also takes a ton of personal responsibility and self control/denial to change habits.

Bottom line, there is a lot of things out there to care about right now, and being vegan is a big change for a lot of people. That, mixed with the extreme (understandable) feelings about mistreatment of animals by vegans, often leads to a feeling of repulsion from investing personal bandwidth into changing the behavior.

That's my opinion based on growing up with religiously vegan parents.

It's simple: if you don't shove your ways in other people's faces, it's fine. If you do, it's not.

I don't care if you're vegan, but if you throw a BBQ and man the grill but don't cook any meat because it's not what you want, you're inviting criticism.

I generally try not to bring it up, but I know folks that've resumed eating meat and we're welcomed back with high-fives. This argues against the "preachy" argument in this thread. And people don't get criticized the same way over eating unnutritious fast food all the time. My view is that some people feel criticized by other folks' different life choices. When Alice to be in an out group, Betty is confronted with their own life choices.

I think its the extreme. The idea of reducing meat consumption over eliminating it is not met kindly by many vegans and vegan communities. I also see a lot of down play of the nutrient challenge discussion. Now like anything on the internet the extremes tend to be the most vocal. I have personally known vegans who are pretty happy if people are even reducing meat consumption at all or being lacto/ovo pescatarians or such. Its really bad as sometimes the message is if your not going to go full on vegan than your personally responsible for destroying the planet (much like all responsibility for palastinian suffer is because joe bidens the one doing the genocidin) and you might as well eat meat at every meal. The reaction of this for non vegans is very often F these folks and you know what I think I will go out and have a triple bacon cheese burger right now because they taste great.

Because strident, belligerant activists don't raise awareness, they just make people hate them. I'm sure there's a generalizable lesson in here somewhere.

Same reason people who love fossil fuels hate people who are worried about global warming