All life is supported by displacing or ending others. Even if you don’t view plants as ethically problematic, the agricultural practices to feed civilisation, by definition, must upset the natural ecological balance and harm animals.

The reason a vegan doesn’t feel upset about eating produce is the degree of removal from the animal harm. They don’t see the deforestation or destruction of wetlands or the damage done by pesticides or in fertilizer production. It’s no different than an omnivore not feeling guilt when a butcher kills an animal (even if they wouldn’t do it themselves).

This harm has always happened since we developed coordinated agrarian societies. The most ethical stance is that humans should return to their natural ecological niche, hunter-gatherers with minimal reliance on agriculture.

However, veganism isn’t possible in such a society. The ability to supplement the human diet with plant based alternatives at scale requires disruptive agriculture. Thus strict veganism* in this lens is inherently self defeating.

*The vegan concept of harm reduction isn’t impacted here, there are still lots of reasons to go plant based