I have my own speculative reasons about why Viking fans have turned on Childress.
Mostly, it's a part of Viking fan culture. Viking fans always believe the team has the talent on the roster to win more than it does, and we blame the head coach for holding the team back. We blamed Dennis Green. We blamed Mike Tice. And now we blame Brad Childress. We complain about the head coach's decisions and ineptitude after wins as well as losses. It's the way we are, for better or worse.
Viking fans also got used to seeing great offensive performances during the Dennis Green and Mike Tice era. Even as personnel changed again and again, the offense was successful. Now the offense struggles for everything--the receivers always seem covered, the plays seem uncreative, and completing passes for first down just looks difficult. Childress came in as an offensive coach, so he gets the blame for that. He doesn't get the credit for the defensive turnaround: if he were a defensive coach, we might appreciate what he's done and be calling for changes in offensive personnel and coaching.
I think Childress' reticence with the media is overhyped. Bill Belichick is no media darling, but Patriot fans like him because he wins Super Bowls. Mike Tice was very open with the media (was he too talkative? We'll have to travel to Tough-Guy Town to answer that), but he wasn't a popular coach during most of his era (there wasn't mass disgust at Tice, but I had many conversations with Viking fans complaining about him). Media members may dislike Childress for how he treats them, but I don't think fans care about that. Most Viking fans dislike Childress primarily for the performance of the team in games: the offensive ineptitude, the questionable decisions, and the mediocre record. Childress' personality may take away any benefit of the doubt, but it's the team's performance under Childress fans are really concerned about.
At this point, I think it will take winning a Super Bowl for Viking fans to come around to liking Childress.
Seifert makes one odd remark that I must note. In contrasting fan feelings for Childress with fan feelings for the other pro sports teams in the Twin Cities, Seifert writes that
"In the Twin Cities, pro sports fans continue to accept Kevin McHale's Millen-like attempts to resurrect the NBA's Timberwolves."
It has been years since I spoke to a Timberwolves fan that thought Kevin McHale has done anything other than a terrible job running the Timberwolves. I have conversations with fellow Timberwolves fans who despise Kevin McHale, and we talk frequently about our desire for him to be fired, for the Timberwolves to move on without him. There's nobody around here that will defend McHale's record (certainly not after Kevin Garnett won a championship just one year after McHale traded him). But there are far fewer Minnesotans that care about the Timberwolves than care about the Vikings, so our disgust at Kevin McHale gets less attention than our disgust about the Vikings. But to the extent that any of us "accept" Kevin McHale running the Wolves, it is just that we've resigned ourselves to the fact that Glen Taylor won't fire him no matter what we want.