I refuse to deal with anti 2A companies myself. I have yet to see any proof that PayPal is antigun.
The business decision to not accept gun related transactions certainly may not please any of us, but it does not make them anti gun.
I think a big part of Paypal not wanting firearms related transactions has to do with the variety of state and local laws regarding such items. Just like with Native artifacts, some things can be sold and then some people will sell things restricted for sales without much concern. They don't want to take part in those transactions. To me, it looks like a CYA type of deal. Probably a big reason why people on forums that accept Paypal say to use the gift option.