Halacha

Question

Dear Rabbi Abadi, You wrote beforehand, """"The nodah BeYehuda says in one of his Responsa, "I don't usually look at the opinion of Rabbis in my generation, nor in the previous generation. I have the Gemara, Rishonim, and Shulchan Aruch. ....Besides that....why should those Rabbis opinions be better than mine." He was giving us a real lesson there. AA"""" So I was wondering then what would be the problem if a modern day rabbi (assuming he's qualified, or perhaps you can offer a definition of what qualified means), would disagree with a purported quote from Ari, or a particular kaballistic interpretation of a Gemara such as a prohibition of a pregnant woman walking on nails?? Thank you, George