Which don't apply to shows like this as the person calling in isn't eligible to win anything and the show doesn't charge people anything to take part.
The only laws governing shows like this (that matter to viewers) are ones originally directed at game shows that prevent them from misrepresenting the vote results. Those same laws also require they take reasonable steps to ensure the voting is fair which, as someone mentioned, is why you see the fine print at the end of such shows that actually reads something similar to: "The producers, in consultation with an independent vote management company, reserve the right to remove votes identified as having been cast in such a significant block, either by technical enhancements or otherwise, that could unfairly influence the outcome of the voting." which just discloses they have to discard voting done by bots and such.
When someone is eliminated or revealed as the winner it's a safe bet it's because it's what was in the vote tallies.
Manipulating the votes is a bad way to get what they want as if that came out, there'd be no way to defend it and it'd cost them a hell of a lot more than having to put Taylor Hicks on a few posters. Plus, Telescope handles voting for lots of things beyond reality shows, some being legitimate contests. Allowing votes they collect to be manipulated or misrepresented would likely end up with them being sued into the ground if it was ever discovered.
Why risk it when it's much easier to manipulate the viewers into voting the way they want them to? It's trivial to have the sound guys work less at making a certain contestant sound good, have the lighting or camera guys make them look bad, edit their little promo packages so they come off offensive or idiotic, tell a contestant the song they thought they were going to sing didn't clear at the last minute so they have to do something else without rehearsal, have the judges say someone who is good sucks over and over and over again or any of dozens of things that can sway viewers towards the results they want that would be very hard to prove was intentional.
Also, depending on what the issue was, it may have affected American Idol as well since Telescope handles their voting as well.
As to the merit of such shows, they aren't in the same class as The Real World or Honey Boo Boo. They're at least marginally about people with actual talents and skills beyond simply being trainwrecks of human existence. I like music so I watch them. But these days I only watch them on the DVR so I can skip all the sob stories and judges' egomaniacal ramblings so they're tolerable, which means I don't vote.