1. Your first Seattle Mariners comparison is a complete embarrassment. A 15 game segment in a 162 game season is hardly comparable to the success Tennessee achieved within the regular season, this year. It would be more akin to Tennessee fans touting a 4-0 start to the basketball season as being anything meaningful.
2. I bet there is a faction of Mizzou fans that still reflect fondly upon being #1 12 years ago. They aren't taking that excitement to their graves most likely, but neither will most Tennessee fans 12 years from now. It's still fresh in the minds of fans, and for others to crap on it as if it mattered not one bit is really just poor taste and ignorant. Mizzou fans talked about that ranking for a long time, I can just about guarantee it.
3. I don't really disagree with much of the rest of your post. Of course, it works in reverse, too. You don't particularly like Barnes or see him as a good coach, so anything he does is under a microscope, to you. He would have to overachieve in the grandest fashion to win your approval because you already have a preconceived opinion of who and what he is.
No one with any sense is pretending like this past season ended the way they hoped, expected, or even that the season was an overwhelming success worthy of reverence for the next decade. But to pretend like there weren't some watershed moments for our program is foolish, as is the idea that people shouldn't still hold those in high regard just 3 months after the fact. I'd suggest you remember the alternative is much worse and appreciate the fact that you had a winning product to cheer for from November to March instead of trying to convince everyone else that the end result means none of it really mattered.