What is there to defend? You cannot analyze a metaphysical claim scientifically. You just can’t. It’s impossible.

Your idea that if something isn’t subject to scientific methodology we should just reject it is pretty dumb, to be frank.

“Does your wife love you?”

Hmm..not sure. I’ll have to rig up some scientific experiment to determine it.

“Is this painting I did good?”

Hmmm… let me run a few scientific tests to determine that.

Hell, the proposition “All synthetic claims should be subjected to scientific methodology” is itself a synthetic proposition that you haven’t subjected to scientific methodology.” It’s just totally foolishness. Educate tourself