Unprofessional MD...but I still got an offer...what to do?

Hi everyone,

I'm a current senior at a (just barely) semi-target. I recently interviewed with a MM bank for a part-time internship in a group focusing on a region I'm interested in. After one interview with an MD, I received an offer. The issue is that this MD was by far the most unprofessional, disrespectful interviewer I have ever encountered. I won't go into too much detail, but just to give you a taste: I had to spend the first 5 minutes of the interview convincing the MD to change his mind about not wanting to interview me (he didn't even look at my resume). When the interview finally "began," he didn't ask a single cultural or behavioral fit question, just jumped straight into technicals and continued skepticism about wanting to continue interviewing me. Toward the end, he was reluctant to even let me ask questions and I wasn't able to gather much about the firm's culture as a whole. Anyway, I ended up receiving an offer just a day later, but the interview really killed my enthusiasm and, to add on top of this, the role is unpaid. Some of you may believe that the interviewer was playing "bad cop" on purpose here, but I assure you this really did not appear to be the case; he completely lacked manners.

The only reason why I am still considering this role is because I feel that more IB experience would be good for my resume and I was told that I would rarely interface with senior management in this role; I would primarily work with analysts/associates. They say that MDs build the culture of the group, so I'm concerned that this whole group may be filled with toxic people. Should I reach out to analysts or, perhaps, HR to get a better gauge of the culture? I would appreciate any advice/guidance on this.

Thanks.