The answer is twofold. For one, you already do things that don’t have a direct, measurable impact, such as voting: you do that because it matches your beliefs.

The answer is twofold. For one, you already do things that don’t have a direct, measurable impact, such as voting: you do that because it matches your beliefs. As soon as you make up your mind about something, it will become part of your moral compass and influence your decisions. If you happen to conclude that intelligent beings deserve to live (and do so with a minimum amount of dignity), it would be disingenuous to your own morals to keep on eating them or tolerate their abuse. The second part of the answer is just a meta-observation: at the end of the day, nobody but yourself can’t judge you. At some point I got to value being able to look myself in the mirror, and part of that is being honest with myself.