Most Helpful Guy
Maybe they think girls are more likely to sleep with jerks and are hoping that by self-identifying as an asshole, it will get them laid.
Most Helpful Girl
By making themselves look bad from the start, you can't blame them once they show their real faces. If you accuse them of being insensitive later on, they'll tell you they warned you in the beginning and you proceeded to have some kind of relationship with them despite their initial warning. So all the blame is taken from them and you are the sole person to blame for your unhappiness. My advice is to steer clear of these type of guys.