This phrase is meant to express support/encouragement/respect for another person’s decisions and habits. Some people use this phrase at least as often as they take a crap . Coincidentally, the two are functionally equivalent.
“If Mary wants to give herself a clitoral piercing with a staple gun, then hey – more power to her.”
“Well Hank, you may be a wife-beating nutcase, but more power to ya if thats your prerogative.” (speaking of which: misuse of the word “prerogative” may have its own special place on Detestable Phrases)
It’s almost as if supplementing an otherwise derisive or critical comment with “more power to you” removes any negative appraisal of the situation. Perhaps it was originally intended to suggest that it’s empowering to do something bold or that runs against convention, but like so many expressions, it was hijacked by dipshits. In fact, the phrase is so meaningless, I’m not even sure what I’m angry about. All I know is that if anyone declares “more power” to me, I’m going to stab that person in the kidney.