I honestly can't understand why he would pledge himself to the Horde unless he literally had no clue what they were about and was relatively unexposed to it's wider workings and operations. They share a passion for the martial aspect like the Horde sure, but defense of home? Has this guy even met Hellscream or have any idea what he's been having the Horde do so far?
Ji just seems remarkably naive to want anything to do with the Horde, particularly after what they did to Theramore. That's the kind of people he wants to ally with? An organization largely bent on the utter conquest of the world who won't bat an eye at slaughtering innocents or using the most detestable and indiscriminate methods to win? I don't care if Vol'jin or Baine represent the loyal resistence so-to-speak, the fact remains that the Horde is mostly centered around factions who simply don't care who they kill, how many, or how as long as they win.
Secondly, the Rexxar example happened in another time under a completely different Horde, one that was actually concerned with building a homeland and defending themselves from blatant aggressors like Daelin Proudmoore. If they joined with Thrall's Horde, that would sound legitimate as they embraced many of the aspects the Firepaw faction holds dear, but now? That Horde no longer exists, it has been almost entirely subverted to bloodlust, treachery, and an unquenching desire to conquer which is almost completely inimical to what Firepaw and his faction is supposed to represent.
Is Firepaw in fact a visionary who seeks to mend that which is broken from within, or is he a naive fool who had absolutely no idea what he was really pledging himself to?