Just as the Geneva conventions are about the conduct that's wrong in war no matter whether it's done by you, your allies, or your enemies, free speech is about the conduct that's wrong in intellectual disagreement no matter whether it's done by you, your allies, or your enemies. Because free speech is more often opposed than supported, I used to think it was a goal, but now I see it's just a tactic for achieving your goals. Like using poison gas and torture, or slaughtering prisoners and non-combatants, trying to force your opponent to be silent is a tactic that's used by people who only care about winning.
They fail to see that harsh tactics do more than encourage their enemy to use the same tactics against them. Harsh tactics make their allies wonder if they chose the right side. The Jacobins launched the Reign of Terror to support the very best causes—as a result, democracy failed and feudalism returned to France.
To go full Godwin, free speech supports your opponent no more than the Geneva conventions supported Hitler.