Because the gun manufacturers aren't doing anything illegal, whereas running a service which creates CSAM is, and so is distributing CSAM. The tortured equival

Because the gun manufacturers aren't doing anything illegal, whereas running a service which creates CSAM is, and so is distributing CSAM. The tortured equivalent analogy would be if gun manufacturers ran a service where they themselves would murder somebody with their guns whenever someone posted a tweet with the victim's name