And there's no instance where something is clearly not morally ambiguous? A moment when realpolitik fails?

You can't tell me that there isn't something out there that you would never compromise on.

Everyone has a line. Once you find it and hold it, now you're the hypocrite pushing for Realpolitik when you can't follow it.

Realpolitik has every bit the capacity to be it's own religion, the moment one places it on a pedestal. That's not necessarily a negative, however, it's just an admission that Realpolitik isn't as special as you may think it is in the world of ideals, when one makes an ideal out of Realpolitik.