In the case of companies, they may want to avoid liability, as well as avoid having their product associated with specific political parties.
Not, of course, a problem Fender would have with someone using their amps to play political songs. Or at least not one they would address by trying to prohibit that.
I guess part of the issue here is the specific, individual anthropomorphism of these instruments. They have names, some of them have pictures and back stories, hearing a particular voice sing something nasty one might go, "Oh my, what Delilah just said!"
But, I guess once more control is available, once we get to the point where virtual singers are totally human-sounding and totally customizeable and no longer have recognizeable vendor-associated individual identities, the issue of liability will seen as less realistic.