Yeah...this is bullshit.

First of all, I rarely ever call this out and usually let it slide, but I disagree so vehemently with OP's point that I'll obnoxiously say that this isn't "we". We don't need to beat anyone. We're not playing anyone. The Steelers are playing the teams. We need to hope that they beat their opponents. We don't need to be up for the challenge of playing a good team like the 2016 Giants, the Steelers need to be up for it.

Second of all, who they beat in December doesn't mean shit. Lose to the Giants but win the final four games, including beating Baltimore to finish 10-6 and with the division (according to the ESPN playoff machine, if both teams go 4-1 with the Steelers losing the the Giants and the Ravens losing to the Steelers, Steelers get the division according to win percentage against common opponents), then they're golden. And that's assuming the Ravens somehow beat both the Dolphins and Patriots. Regardless of whether or not the Steelers beat the 8-3 Giants.

Point is that it doesn't matter who you beat to get to the playoffs as long as you're there. In the regular season, the 1972 Dolphins played a grand total of two teams that had winning records, and zero that made the playoffs. That didn't stop them from going on to win the Super Bowl and become the first and so far only undefeated team in the Super Bowl era. No team is going to come out after a playoff or Super Bowl win and say "We won this because we beat the Giants when they were 8-3 in Week 13 back in early December!" Because that makes absolutely no sense.