The fact that you are assuming someone wants to use Tor on Lemmy to do something illegal shows that you have fallen prey to the idea that Tor itself is illegal or meant for illegal activity, it's the driving force behind many of the pushes to block Tor or even to attempt to extinguish it.

Fact of the matter is Tor is a tool, a tool that like any is not inherently evil or illegal. Tor's purpose also isn't to facilitate illegal activity, its purpose is to provide privacy and anonymity to people who want it. It sounds to me like you have been listening to a lot of those "scary" deep web videos or assuming people use Tor for those reasons and not for legitimate privacy and security reasons, (like for example did you know that Lemmy doesn't proxy images?). This is one thing I really hate about those types of content, they portray the idea of privacy and security as if it's evil or nefarious, or that the idea of hosting your own hidden service is creepy or wrong, it's really gross actually, all for clicks and views, but they push it as if it's real, it's harmful to services like Lemmy which are currently outside of the mainstream and probably are associated with Dark web contend just by virtue of not being Big tech products, for a while I'd heard similar stories about linux too (people talked about how linux is for criminals, glad that one didn't catch on).

TL;DR you shouldn't be assuming that people want to use Tor (a privacy and security tool) for nefarious or evil purposes due to it's reputation with nontechnical people, especially when those people are known for spreading misleading or even wrong information about the subject itself.