NCC1701: yes, those were the days, huh? I've managed to be lucky in love as regards to my diet ;-). Changing my diet has never been an option.
I spent some time on a farm when I was young, and saw the way commercial milk, eggs & etc. were produced, and that was enough for me, even at the local producer level. It's gotten so much worse since... You can't even get raw milk anymore in many places. No more clotted cream ;-)
The film version of The Secret Life of Plants made me queasy about consuming some plant life, but as you say, there are life forms all around / within us all. I considered becoming a modified fruitarian at one point, as it seemed to make the most sense, but again budget & climate intervened. Sentient beings are a good base point at which to stop adding to the menu, I think. I do what I can, and over time, hope that in addition to my own well-being, some other good is being done.
At the end of the day, I really don't subscribe to the notion that humans are above or "in charge of "the rest of the sentient life forms on the planet.