frumnotyeshivish: Some of Perkei Avos is Halacha because it is in Perkei Avos, not because it is Halacha L’Moshe MiSinai. Other things (such as (I would think) “Sonei Es HaRabbanus” or “Lephum Tzara Agrah”) are not “Halacha”.
The concept (which you probably mean “Nitnu Reshus L’Chachamim”, not “Lo Bashomayim He”) puposely has very narrow application (perhaps Chol Hamoed, maybe others). Lo Bashomayim He is a completely different idea, in which bais din is given the right to Pasken within the framework of existing Halacha. It has nothing to do with making new Halacha, Chas V’Shalom, and certainly has nothing to do with “morality”. Tanur shel Achnai (the classic example) is a Halachic, not moral, issue.
If you define Halacha as “morality”, that is perfectly understood. Just realize that you are not using the word in the way other people would understand it. It is like calling an object with four walls, a roof and a door a “cat” because that is what you think a “cat” should look like.