As far as I know, it requires intent to do something illegal, i.e. running an illegal platform for drug & gun sales with the intent of providing that service.
Just running a tor node wouldn't be touched imho, but yeah, it's a terrible idea in general.
Ah, sorry, I didn't mean to imply guilty-till-proven-innocent (I don't think that's how German law works). Merely that a prosecutor is going to present some evidence to try and imply your intent was illegal ("67% of Tor traffic is illegal therefore the accused is guilty!"), and you better hope your arguments will be more convincing.
Basically it makes Tor nodes too much of a legal gray area to safely operate.
I talked to a lawyer friend of mine and he confirms that the law is pretty broad, but not that bad. A person using TOR won't be targeted on this, they already have laws to get buyer & seller.
Just running a tor node wouldn't be touched imho, but yeah, it's a terrible idea in general.