I don't think anyone worth listening to considers dark matter to be a Universal Truth or anything. It's a crappy theory that needs better experimental evidence on the micro scale. It's just that all attempts to find that evidence have turned up nothing. (Except DAMA/LIBRA, the bane of the previously mentioned colleague's days and motivating factor for the experiment in question... but nobody actually believes them, so let's value their reports at "nothing".)
The biggest problem is that all alternatives to date are worse. They all have problems, problems of equal or greater severity than dark matter. That, more than any other reason, is the reason dark matter is still the leading theory.
I do strongly believe we should work on the advancement of non-dark matter theories. That's how you lap the current leader, after all. And neglecting alternative theories was what got us into a couple decades of string theory stagnation, a mistake we'd be wise not to repeat. If a new theory or new evidence for an existing theory emerges, dark matter will lose mindshare amazingly quickly.
There is, of course, a "nightmare scenario". The WIMP carries a weak charge, by definition. It was dreamed up that way to make it detectable and have a presence in the universe. (And there may have been a theoretical preference; I wouldn't know, I've always been an experimentalist.) But there's no reason it must carry a charge, weak, strong, or electromagnetic. That would make it really quite invisible to experiments. This may be the universe we live in.