Sorry, this is conflation of terms like 'free' and 'open'. I see this confusion in many areas (like political thought), not just Bitcoin. Free and open in civilized societies (or where that is the goal) doesn't mean 'do whatever you want.' That isn't freedom, but hellscape.
If we don't remove the filters, they can only force things in via out-of-band, which only works with overly-centralized mining... which is something we can't have (and need to fix) anyway (and such efforts are heavily underway).
We don't actually have to cater to the attacks just because we can't stop 100%. Do you use an email service with spam filters?