First things first, let me commend you on your verbose argument. However, there was no need to flare up like a Beta fish, least of all at my pal knuxiechan who happens to be a pretty kickass person.
Human sexuality is a complicated and many-splendored thing but please understand something very important.
Everything is potentially offensive. Don't like it? Deal. People are going to go through life offending you left and right. You gotta bugger on. Hell, I AM pretty offensive myself. But I stand by my opinions and beliefs. While I respect your special snowflake attitude, I find the fact that you're willing to hash out a verbal lashing but not take it to be particularly infuriating.
It doesn't matter how people choose to interpret a word. Language is fluid, yeah, but only to a certain degree. Language and word meaning can only be changed if a vast majority agree on a new definition of a word [for example-- gay didn't primarily mean homosexual until well into the 1980's, because pop culture as a whole and the academic community agreed on a meaning].
I hate to tell you but the standard by-the-book definition of bisexual is being attracted to two genders. Two. That's what the entire prefix of BI means. TWO.
I won't hold this against you because I doubt you ever took Latin. It's one hell of a course, avoid it at all cost. Dead languages are dead for a reason.
Honestly the word pansexual itself is a clusterfuck of languages. Pan itself isn't even a latin prefix. So yeah, super weird. But the word pansexual means 'attraction regardless of gender'. Which can be extended to identity as well.
If you like the boys and the girls and just that, you are bisexual.
If you like beyond the binary [including trans/nongender/whatever] then you're pansexual.
Mind you these words can also extend to romantic attraction.
Human sexuality is complicated as fuck.
But that's beside the point.
Please don't fuck with my friends. You will be schooled.