I really do not see what the deal is concerning Doug. As far as I have seen from the show (and I have watched every second) , he has not done anything for anyone to think negative about him. Doug looks like Brad, a gentleman like Brad, from Emily's experience with Brad obviously she is sceptical. No one goes on a date with a woman/man even for the first few times and tells the other of their fault (which we all have). the other finds out the faults little by little as time goes on, and we really do not see our own faults.
Doug may be in the mix in dramas in the house, but the drama is usually not his starting nor his fault. With Chris, Doug is just a passive one and Chris is beating up on him. Infact Doug is really being the adult in the room. With Arie, we know Arie was playing on Doug's insecurities (no rose you go home date) hoping it will give Doug a terrible date which will send Doug home. Arie kept on winding him up and when he got frustrated, he may have given him a piece of his mind etc.
Doug was the one caring for the other father and from the little we've seen so far, he seems to take care of the others. Him not calling his mom his mother is no big deal. Some people who are given up for adoption still prefer to refer to the woman who brought them up as their mother and are not interested in their biological mothers. Doug is by no means odd in this aspect. Why should he want to be associated with his mother who was not interested in him. He has moved on and does not see her as his mother. end of story. That does not make him a villian, woman hater, psychologically damaged etc etc because of this. Usually the opposite occurs and people like this turn to be very resilient, strong, determined and focused as they have learned to struggle and overcome situations.