First of all, it wasn't impeachment about oral sex, it was impeachment about perjury and conspiracy. Sounds a little more important than oral sex.
Secondly, it isn't about the "Clinton defense", it's about what a former President did in the exact same type of situation. Or is it your contention that we should just ignore those 8 years completely? I'd like to but those 8 years led directly to the worst attack on US soil ever. Oh yea, thats right, it happened on Bush's watch so it was all his fault, in January of 2001 was when the started planning, training, traveling over here (ignore the arrest of Atta in 1999, that was Clinton's watch and we are ignoring the man in the corner for those 8 years). Just because they started planning it in what 1993, 1994, those years don't count.
Personally, I get tired of the "it's the Republicans trotting out the Clinton Defense" defense as if that repudiates the points made. Clinton didn't exist! Talk about the emporer having no clothes.