Well in the game the other day, one of the interceptions it was tipped. So that doesn't really count.
Indeed. The point is that Plummer has a history of failing when the team needs him the most. Considering that Denver used to have Mister Fourth Quarter himself, John Elway, that isn't exactly endearing to Plummer's status as starter.
Furthermore, saying that the team's record is proof that Plummer shouldn't be benched, then saying that the team is making Plummer look bad, makes no sense. It's one or the other--either the team is doing well because of Plummer, or it's doing well in spite of Plummer. It can't be both. At this point, it's the latter: Denver's winning games when Plummer isn't being asked to carry the team. Those 7 wins are largely the result of the defense being excellent at preventing opposing touchdowns.