There are more positives to stealing from a bank than negatives but that doesn't mean it's legal.
Eh, yeah, but that's not really the same thing here..
Negatives are far more severe and long-lasting.
Hm.. depends on the negative.
Bedhair, spoiled turnips, and weeds?
Those are not too bad. Go get fixed up at Shampoodle, ask for a garbage can, pull out the weeds (and get a cool badge!)
Losing villagers and random move ins?
Yeah, losing a villager is sad, but it's not sad enough that I can say it's long-lasting considering we have options. Cycling to get them back, resetting your town(though there aren't many who do this, this is an option if you don't want to cycle.., and find a replacement.
Can I ask how random move ins come from TTing?
Environmental Destruction?
If you know you're going to TT or be gone for a while, having the Beautiful Town ordinance wipes this problem out. You'll have weeds to pull, but your garden won't be destroyed or anything. Trees and bushes don't die either.
Meh. Your argument may be valid, but I feel like most of these problems have solutions and it'll all be okay in the end.