Just to remind myself, I went back and read the recap from nfl.com archives, and it describes that exact mindset as a result of the 2001 and 2004 losses.They beat the Steelers in 2001 as seeming upstarts that had no business coming into their house and beating them in the AFCCG on their own turf. Then they did it again, in a season the Steelers went 15-1, in 2004 and fucking embarrassed them.
That season also marked the 'dynasty' talk, which Steeler fans don't like hearing be ascribed to anyone other than their own franchise. Steeler fans I know also hate the Cowboys and 49ers for similar reasons, but before NE they were the royalty of the AFC and their status has taken a ding. My most ardent Steeler friend relented after our most recent drubbing of them and the new ring and finally admitted how amazing Brady and the franchise are, but he still had to add 'call me when you get six'. It's almost entirely about status for most Steeler fans I know.
https://web.archive.org/web/20060116203921/http://www.nfl.com/gamecenter/recap/NFL_20050123_NE@PIT
And this link also describes that the 2004 Steelers believed the Patriots were taping the Steelers defensive signals during the regular season loss as well. So there were two heartbreaking losses, and the suggestion of cheating.
https://www.behindthesteelcurtain.com/2009/7/8/941076/the-12-most-heartbreaking-playoff