After what USC did to OU in that game, there is no way you can ever convince anyone that LSU would have beat USC. Hell, even LSU knows that.
It's frustrating. Michigan and Nebraska fans argue about 1997, Miami and Washington fans about 1991, etc.
You've forgotten your history. LSU beat OU by 7 and USC beat a lesser Michigan by 14. LSU beats the #1 team all season and USC beats a reasonable but lesser Michigan team and folks want to give it to SC. LSU earned their share and has the better claim and what SC has done since is irrelevant to that discussion.