1) Even if a user is 'found out' in the community, there's nothing that can be done to prevent them accessing mods online. Period.
2) If someone does harass you with them, report, blacklist, move on. Why let it ruin your life?
3) It's all client-side, not server-side. It's literally the same thing as imagining someone naked. They're clothed, but you can 'see' them naked. And as long as you have the common sense not to tell them about it, everyone's life goes on.
4) Unless the game files are completely overhauled, literally anything and everything can be changed and modded. There's no such thing as "safe" apparel in the long run.
5) People that use the mods and never share/talk about them/shove it in your face aren't a problem. The problem is the jerks using it to harass others, and they'll find ways without mods to be A-holes.