At first I thought "disgrace" was to strong a word, but the more I think about it, the more it seems to fit. For a historically good player like Peyton Manning, and for the team that has gotten through so many close games by the skin of their teeth, you need to show yourselves the respect of playing hard.
If they were 13-1, then yeah, you can rest if you want because you aren't on your way to history. But it just seems disrespectful to the fans to not 'swing for the fences' in this situation.
Not to mention, a lot of people (including myself) feel it is actually harmful to rest your players so much. They fall out of rhythm and lose momentum.