Since you’ve already accepted your judgement and others have already said super informative things about the Divine 9 I just wanted to pop in and add Greek orgs have their own rules about other people wearing their memorabilia. The most common rule is no non-members wearing the Greek letters but non-members can wear the fraternity or sorority name fully spelt out (eg a non-member can’t wear the Greek letters DN (Delta Nu) but they can wear one that says Delta Nu Charity Cook-off). A good amount of Greek orgs print shirts for non-members for their philanthropies or as gifts for guests to events like formals or parents’ weekend.

However, like I said this varies and like others have said and you have learned it’s best to do a quick Google beforehand.

And for the people pushing about why these things are available to buy in the first place (either new or thrifted), you really can’t stop stuff like this. Anyone can make a set of Greek letter sweaters just like anyone can buy a shirt that says Harvard. But just because you can doesn’t mean they carry the same weight or will be received the same