Again - every PayPal transaction has both a buyer and a seller. So, if people can buy something with PayPal, someone else is selling that thing.
If no one was allowed to sell such things via PayPal, then there would be nothing for anyone to buy, so in effect buying such things would not be possible either.
If you mean PayPal might shut down a seller's account due to violation of terms or too many chargebacks and such, but would not shut down the accounts of the people making the purchases? I imagine that's correct.