Well, logically, they may have made the right call. If the ice was just too thin, their vain attempts could very well have gotten more people drowned. It makes sense that they would not want passerby's running in trying to help, and then falling in themselves.
However, emotionally, it seems like they should have at least tried SOMETHING, even if it has little hope of working.
Everyone has their own threshold for danger and risk to their safety. But there is a fine line between bravery and foolishness. There was a time back when I was a cop, I was chasing a shoplifter (stole a pair of bluejeans). The guy ran like a a gazelle. I kept up with him for a long time until he ran across a busy 6 lane freeway. I said screw it, and let him go, because my life is not worth a $40 pair of jeans. If he had been a murderer it would have been a different story. There are plenty of guys that would have kept chasing, and just as many that wouldn't have even tried to catch him (lots of fat, slow cops) but that's their choice to make.