Calling what Trump did to Iran unconstitutional was not useful, necessary or particularly "conservative". It may violate his libertarian streak, but that doesn't justify calling it unconstitutional. All he had to do was keep his mouth shut for a few days - but he couldn't do it. In short, it was just dumb.
I'll add that is where Ron Paul goes way off the rails. Iran with nukes is no minor thing.
In the light of the fact that I am on the record here stating that Massie is wrong on this:
Massie doesn't see the War Powers Act as legit. In a pretty typical libertarian fashion, he reads the Constitution extremely literally, and figures no way to alter the giving and taking away that it provides - A thing I mostly agree with him on, most of the time.
But the point being, it's a particular bone he has to pick. I expect it out of him, just like I expect him to go off when fiscal matters come up.
Sometimes the dog barks at nothin. It's part of having dogs. But you don't throw the dog away for it. You'll be praising that dog when the bear comes around.