My theory is that Inoda is going to use this information simply to his advantage, it's been established that her mother doesn't like "Cuckito" due to her own personal reasons, whether they are justified or not.With the direction the game is going in part 1, it seems like there won't be any blackmail (using Asuna mom's affair) since Asuna has already slept with Inoda. Blackmailing her by threatening to expose temptuous night might seem plausible though. That being said, I do hope Fujino incorporates some form of blackmail into making Asuna fall.
He could use the video to blackmail the mother into helping him get closer to, Asuna. For example allowing him to come over while her mother is home (As Kirito is not allowed to do this.) Seeing that her Mother likes someone who is a potential love interest for her could sway her even more in Inoda's favor.
Inoda, the mastermind. I think it's better then directly blackmailing Asuna anyway. But, that's my opinion. Win her mind, body and soul. I think is his plan, he's already shown himself to be quite calculating.