I do see your point but unfortunately it isn't against the rules to be a twat.
It's also not against the rules to be wrong and/or stupid.
Also, although I agree with you completely, I'm not sure drawing attention to this type of poster is a great idea. I think it will simply feed their mahoosive martyr complex.
This type of person lives for the chance to 'speak out for the disenfranchised masses', they genuinely believe that they are persecuted for 'standing up for truth and justice'.
Don't give them another opportunity to play the victim.
I know it's hard, and yes, it is important to correct the factually incorrect statements they trott out with such misplaced confidence but, other than doing that, IMO it's best to simply refuse to engage. Leave them to froth to themselves in a corner.
I'm sorry for anyone who has ever been upset by this kind of crap. I have been myself, many times, (I don't often actually take my own advice). You shouldn't ever have to listen to the bigoted bile they spout but sometimes wrong people just enjoy their wrongness too much to allow them to actually hear the truth.