Seth Rogen slams Justin Bieber at SXSW

Seth Rogen dropped by "Watch What Happens Live" at SXSW and, well, he didn't hold back when answering questions. And when a viewer brought up Seth's Twitter attack on Justin Bieber in January ... Seth defended it. "He's obnoxious, ungrateful, and insincere and he puts people's lives at danger with his horrible, horrible behavior," Seth said. His choice words didn't end there either: