The adjective discriminating means someone who is able to know and act on the difference between good and bad.

Synonyms are astute, choosy, discerning, or selective.

The word origins in 1792. It is the present-participle adjective of the verb discriminate meaning “to treat someone differently”.

Maybe he thought they were discriminating against her.

The most discriminating character of Garrick is that drawn by Goldsmith in his poem of Retaliation.

His criticisms about politics are not discriminating.