He's using the same logic as the OP, that Tanner "supporters". If you want to replace a Senior QB who is something of a legend (even if injuries have slowed him down), then the replacement must be Tom Brady. With this type of logic, apparently the senior QB must be a Tom Brady type, himself, or why do you need a Tom Brady to replace him.
The serious argument is, most merely want to give Tanner a chance, to show what he can do. Why don't you play him a series or two in the second quarter of the Boise game (the half where Taysom was 3-14 passing)? What do we really lose? If he doesn't play well, you can always through Taysom back in, but why not at least give him a chance?