Hooray! An unpopular opinion!
Yes, you're right. But your opinion is more or less what The Good Place (fantastic show) was saying. It is impossible to truly be a good person in society. The only way you can do that is by completely leaving society and living on your own. Having hard rules of "You're either doing good or not" means everyone is bad, as you're saying yourself.
There's a middleground. It is not "You are good or bad". Eating less meat helps the planet, reduces greenhouse gasses, and reduces wasted land. It's also horrible for the animals and knowingly exploitive. Those are facts. Now, what you say is true too, but what, should they just not eat at all? I know many vegans do try to grow their own food and do try to obtain everything as ethically as possible.
But it's impossible to live in society and not at least moderately hurt other people/animals/the planet. The clothes we wear, the food we eat, how we get around, our hobbies, these computers we're on, they're all built on exploitive labor. You have to pick your battles though, and you have to try.
Now, you can absolutely educate them, absolutely go for it, let them know. But I wouldn't start with calling people who are trying to make a difference "sociopaths".