Just one thing he said to Oghren in DA:O, calling him a heathen. But, again, who knows. I might call Oghren a heathen, too 
Yeah, I think what Cullen said to Oghren has to be taken in context: Cullen had just been tortured, and Oghren appeared to be making light of his pain, basically told him to calm down about this huge thing he'd just suffered through, and topped it all off with the disrespect of calling him "lad." I don't think Cullen lashing back indicates anything about his overall feelings about dwarves.
Note that he doesn't make any sort of anti-dwarf comments to a dwarf Warden under the same circumstances.
It's possible that he has some sort of bias against dwarves, but what I take from that particular conversation is more that Oghren made insensitive comments at a bad time and Cullen reacted predictably, rather than any sort of deeper indication about Cullen's feelings regarding dwarves as a whole. 