"...pornography and racism on GAB..."
No idea what my settings were on Gab but I only saw a bit of antisemitic chatter along with the same level of anti-Islamic chatter you read on FR on any given day. I don't recall seeing any porn on there but I wasn't seeking it out. That is just an excuse IMO if that is the reason for their service interruption.
I haven't seen a clear statement by the owners of Gab stating what justification was used by the host to close them down. And yes, it does matter, even if it is suspected there were other reasons.
I have never seen porn on there, but understand that it is there if I turn it on in the settings. I did see antisemite stuff and was horrified, deleted my account, and left. Andrew Torba sent me an email asking me to return and explained how to setup my account so that I would not see it. I think those instructions are now given when one signs up as Ive seen many messaged with ithe instructions when they make their first post.