When I went on a vegan trial, I discovered a new thing called "fruitarianism" - people who eat just fruits and such that fall from plants "willingly." I really had to think about this. Plants are alive like animals, are they not? When we harvest plants we kill them do we not? I think this is a valid contemplation, esp. when one of the main reasons many people seem to go vegan is to avoid killing their "friends."
Maybe all we can do is reduce suffering as much as possible. It may not make sense to try to not kill anything i.e. just taking what's openly given like fruit and some nuts, because harvesting carrots is killing carrots (and bugs). I think we can do much, much better than factory farming without becoming malnourished.