The 75% of people who know for sure that Bubba stepped out on Hillary! will not be more sure after seeing a tape. And the 25% in denial can get into fits of moral indignation about yet another example of character assassination against their heroes, the Clintons.
And Bubba would like nothing better than to have us all looking at his exploits. He's that much of an exhibitionist.
You're probably right. What would be the point of her foes getting ahold of it to "use" against her? Everyone knows what he does anyway.