PayPal is not a public utility, as much as you’d want it to be one. Until the government determines it is one, then the rules of public utilities don’t apply. Once again, regardless how much you wish it were so.

It shouldn’t be forced to do business with you because it is a private business and not the government.

It also is nowhere near a monopoly. Plenty of payment processors exist. Another comment here literally talks about new ones springing up.

It is equivalent to the bakery store in your example.