How would you feel about the fact that they made the Jim Carrey movie and put it where you could see it?
I don't think the Morisetteian irony of watching a movie that's equally fucked up in its premise as you found out your life is would move the needle much. The rug would've been pulled out from under you and this wouldn't cause more than a wry bored smile a couple of weeks later when the shock has subsided a bit.
Per your definition, the effects of loyalty are always per se negative. I don't doubt that in many situations this is true. I don't think it's always true. And a lot of it has to do with how we socialize. We need strong bonds. On a purely rational level, I'd be inclined to agree with you. We aren't very rational though.
If my hypothetical friend, out of the blue, got drunk, got behind the wheel, and ran somebody over, many people might turn away. If I stayed by their side, helped them arrange themselves in this new life of guilt, helped them make restitutions, and kept them from sliding into isolation and depression, my loyalty could be seen as a force for good in a bad situation. I could still donate to cover the victim's medical costs or funeral. There are bonds that keep us together even when we effed up.
Now, if I had willfully ignored all signs of alcohol abuse before, I think I'd be back on your page. So what I'm saying is we can create scenarios of loyalty with good outcomes. So the categorical dismissal as something negative isn't true.