The only way my block list could be effecting others is by preventing them being instanced with cheats or griefers, in which case I just did them a favour. It could also prevent griefers/cheats from being able to wing up but I don't care about that.
It should be clear that not everyone has precisely the same standards and claiming to be doing others a favor by making it harder for those who are unfortunate enough to be instanced with you to instance with those whom you have unilaterally declared unfit to play with is about the worst sort of thing I can envision one player doing to another in a multi-player game. It's both grieving of the highest order and were it not (to their discredit) condoned by Frontier, I'd consider it a cheat itself.
I'd block your CMDR in game myself, but that would simply exacerbate the instancing issues you are helping to perpetuate, and we have far more than enough of that already.
the second I can't play a game on steam is the second it is not fit for purpose.
Something you should have considered before patronizing Valve and using their Steam client.
The odds of them just denying you access on a whim is quite small, but you absolutely did agree to terms to that effect.
I just don't understand the pedantry on this subject.
The degree of ownership one actually has is the crux of the argument some people seem to use to impose their whims on others.
Stigbob, for example, seems to think that because he paid for access that he can play the game, in Open, and try to carve out his own group by attempting to arbitrarily exclude others with the block list.
That's banning for cheating though, that could be argued in a court of law as you say because of EULA/TOS.
The EULAs and ToS almost always include clauses that allow them to refuse service at will. No doubt that some of these aren't enforceable in some areas, but many of them are at least as enforceable as banning for cheating.