The whole "right to free speech" thing is irrelevant.
People have the right to publish works glorifying child abuse, genocide or Clippy the Office Assistant, it doesn't mean that they're exempt from debate or criticism.
If you decide to exercise your freedom of speech by saying that rape should be legalised, you can expect a strong reaction, and not just from radical feminists.
I'd agree with your overall point but point out that this isn't free speech being irrelevant but instead showing that the right to free speech extends to both sides. If someone posts a "rape should be legal" article, that's their free speech right but it's also my free speech right to disagree with them and argue that rape should be illegal. If one "rape should be legal" author finds themselves drowned out by dozens of people saying "keep rape illegal", that's not infringing on his freedom of speech - it's everyone exercising their freedom of speech as well. (Your right of free speech doesn't mean people have an obligation to listen to you.)