There are already limits on free speech so that's not a great counter argument.

There can be legal consequences to some speech, but our voice boxes haven't been flashed with firmware that limits our ability to use certain words. This is not at all analogous to what Apple is doing with iPhones. To be the same, it would have to listen/parse everything you say and filter out the offensive parts so other people don't hear them. It would also need strong technical measures to prevent you from flashing your own voice box firmware that allows you to bypass Apple's restrictions. If you can point to an implementation like that, then you may have a point, but I'm entirely unaware of the existence of such a thing.