My sister has bad taste in men. What should I do to help?

My sister is a dean's list student. She is a very smart girl, but she's also a fun loving girl, but a good girl. I saw a guy she's seeing on Facebook today and it's been messing with me all day. He's a douchebag with a million dumb chest tattoos and he's in every picture shirtless posing like an asshole. My mom was a single mother because she had bad taste in men and I don't want that for my sister. I'm not an over-bearing brother, but this is freaking me out. Is there anything I should do or say? How should a brother handle this?
My sister has bad taste in men. What should I do to help?
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