Didn't he save Vader? That's what kind of ruined the debut for me, it looked awkward to have someone the size of Vader need help from a relatively small, normal looking guy like Blackman.
Plus, I hate it when they use a 'guy jumps out of the audience to help the face' type of debut ... it's no wonder why drunken hicks then think it's kosher to jump the barrier and interfere. "Hey, it got Blackman a job ... maybe if I run in and push over the ladder they'll give me a job, too!"
IIRC Vader was being attacked by, I think, the Hart Foundation. Blackman did some kicky thing and then Vader basically saved Blackman from the security that was coming out to detain him. I remember Vader covering/restraining Blackman to "save" him from the security guys.