Learn Italian: Ci si offende se il tono è maleducato. - One gets offended if the tone is rude.

The verb here is offendersi (to get offended), which is reflexive and already needs the pronoun si. To make it impersonal ("one gets offended"), you would technically need two sis together (si si offende). Because Italians don't like how that sounds, the first si changes to ci, creating ci si offende.

What is the infinitive of the verb being used in ci si offende?

It's offendersi, which means "to get offended" or "to take offense." If it were just offendere (without the reflexive ending), it would mean to offend someone else. The ci si structure tells us it is both impersonal ("one") and reflexive ("gets offended").

Does maleducato mean "uneducated"?

No, maleducato is a classic false friend! It literally means "badly brought up" and translates to "rude" or "bad-mannered." If you want to say "uneducated" (lacking formal schooling), you would use a word like ignorante or non istruito.

Could I say uno si offende instead of ci si offende?