PS - I strongly believe that if ebay and paypal were anti gun that A) ebay would not allow the sale of magazines, holsters, or anything else firearm related and B) paypal would freeze transactions on those items.
(I am a power seller on ebay and they along with paypal have always worked out all the problems I have ever encountered)
I don't think this is an accurate assumption. Even though they allow certain gun-related items, they're still needlessly restrictive, and even that is recent improvement. For instance, it's now ok to buy or sell mags, but of only 10 rd capacity or less.
The more likely explanation for allowing gun-related items has less to do with them being ok with guns and more to do with the fact that there is money to be made. It seems more like they are trying to balance their anti-gun stance against the potential profit to be made from the sales of gun-related items.
Look at it this way, if eBay allowed the sales of firearms (with the same stipulation that all buyers and sellers adhere to all applicable laws as is done by gun auction sites like gunbroker, auctionarms, and gunsamerica), it would be a huge cash cow. eBay and Paypal is actually a very well-designed system, extremely convenient, could make the gun auction experience more straightforward, and what's more, you'd have the convenience of buying your guns from the same auction site that you can get most anything else. If eBay fully allowed guns, it would likely overtake gunbroker, auctionarms, and gunsamerica overnight! They know this, but they don't do it. So they try to make what money they can from gun people by selling what they consider more innocuous items like holsters, slings, grips, mags with capacities less than 10, etc.
That said, I have used PayPal to buy gun accessories off eBay, including grips for pistols, holsters, a scope, and probably stuff along those lines; they didn't give me any trouble over any of it.