I’ve only known examples where you’re free to reject anyone for any or no reason as long as it’s not because they’re one of a very small list of protected groups.
138 misdemeanor law: Whoever, professionally engaged in the provision of services, demands and collects a payment higher than the applicable fee for the service, or intentionally, without a justified reason, refuses to provide the service to which he is obliged, shall be subject to a fine.
Some forms of propagation of fascism, communism and nazizm is prohibited in Poland, but I guess it probably would be illegal to refuse service to someone who otherwise declares support for some reprehensible ideas, and does that privately, so it doesn't fall under hate or other laws.