@posthlewait3 How difficult would you find it accepting their arguments that their lifestyle is the "right" one? Probably really quite hard, if not impossible. That's the answer. People find it extremely difficult to change behaviour, especially habitual or long standing behaviour. Especially especially if they are in a defensive position and really especially especially if that position is the norm and not the exception like veganism is.
Whenever you try and understand why hitting someone with your facts doesn't make them change their minds and renounce steaks and cheese, try and imagine if it were the other way around. What started your journey? Probably not someone arguing with you that your current lifestyle is wrong. And even if it did, did you turn around to them and say "damn, you are right, I was wrong I will never consume an animal product again starting now!". Or is it more likely that if you had a conversation in a non confrontational open way that it might sew a seed of an idea in that person. They then might go home and watch some documentaries, try some new foods out, read labels a bit more and make some different choices. Their journey has begun and just because it isn't all carried out under the glare of a disapproving level 7 vegan doesn't make it any less valid.
I get that waiting for the world to wake up is hard. I'm the same with waste, over consumption, climate stuff and god forbid you put the wrong thing in your recycling bin while I'm there! But spouting facts at people just makes them defensive and turn off. It's frustrating but if we want to advocate effectively then we need to be better at effecting behaviour change in others than we are now as a community I think