You are missing the point: PayPal does NOT provide any specific reason for the termination, so there is NO protected class as you cannot prove they terminated an account for speech, race or gender.
Giving no reason, absent a contractual or legal requirement to provide one, falls far short of offering up a blatantly illegal explanation. Even so, companies have clearly been found guilty of illegal discrimination, even when they went out of their way to hide their unlawful motivations.