It wouldn’t be nothing and you know that. If you simplify the meat problem to just emissions, sure, it might look small in comparison to cruises, etc. But if you look at it as the multifaceted problem it really is, then reducing consumption will have several effects. Especially, as you exaggerated, if you forced everyone you know to do the same.
The last thing we need is people advocating for these “fuck it” attitudes. Should we really excuse better choices and better directions of behavior and culture just because there’s a “small” effect? I feel like this line of logic can be used to excuse some pretty dark shit.