That's just ridiculous Joe Fan logic. If you pay for a ticket, you can boo and cheer whoever you want.
A fan's loyalty is with a team, not a player - Bob Dole doesn't care about hurting Drew Bledsoe's feelings, Bob Dole only cares about what is best for the team - if Bledsoe is stinking it up, he deserves to hear about it.
How else should the fans voice their displeasure? By not showing up? Yeah, Jerry would love that.
Maybe after Bledsoe's next INT, everyone should just go, "AW SHUCKS DREW, MAYBE NEXT TIME PAL."