If you want my backup you might try re-watching the series, while the Xindi thing may have been inaccurate it was a theory, and regardless its more than most people gave. Half these people have seen like maybe a series and call themselves Trekkies.
I don't devote myself to much, but star trek is my show and I watch it religiously. I make assumptions and theories the same as all of you but in fact the xindi weapon was fired as noted in s4 e3 when everyone is still up in arms about it after timeline reset from s4 e1&2 making my theory bunked, however the events of kirks time (20 years later) may still have altered the timeline in some way.
I'm busy watching it to discover the reset in the timeline but unlikely ill find it as Xindi were not mentioned anywhere else even googling Xindi Xendi and Zindy (looking for common misspellings) I only recovered one mention in star trek tng about a Xendi (not the same) space station and a small footnote where the Borg had a Xindi officer (by appearance only) on board a ship sometime during the Undine (species 8472) battles.
I can however only speculate (that means not a fact btw) that the Xindi became xenophobic after the events of the sphere builders and we haven't seen the last of them it would make a killer short series if not longer (like ds9) about the events that lead up to sphere builders battle 400 years later.
K so I mentioned my (self proven) false theory my new theory and personal belief that star trek is not a complete series yet and even though have a love for the universe as we know it lets wait and see what they bring into play from the mirror universe that may (or may not) alter the enterprise NX class missions everything will be answered in due time
just so everyone is aware "theoretically" does not mean i need fact to prove my theory i need events that lead me to that conclusion and if you were to sit and think long enough you'd speculate too but my answer still beats " didn't you pay attention the whole thing was a hologram that riker played...."