I don't think that slippery slope is likely. There is a world of difference between pornography and controversial political speech. We have had obscenity laws

I don't think that slippery slope is likely. There is a world of difference between pornography and controversial political speech. We have had obscenity laws putting strong restrictions on pornography for a very long time (see 18 USC 1462 - 1468) and they haven't resulted in other speech rights being curtailed, I don't think there is any reason to think this law will be any different.