Bitcoin XT is basically a new bitcoin that is profitable for Coinbase. No one supported it from the beginning. No one will in the future. The original is the one and only, and no fake can best it. Bitcoin XT was never going to be a success, anyway.
I suspect XT has achieved exactly the effect "they" intended it to. I don't believe the real force behind the XT push ever intended or believed it would gain adoption.
Beat the price of BTC down, FUD and "divide & conquer", mission accomplished.
The cost to reputation and credibility of Gavin and Mike H. has been significant. Instead of being merely suspicious behaviour they are now clearly in "cannot be trusted" basket. Not even "trust but verify" with those two, default position is "don't trust, don't even bother verifying".
I've felt that way about Hearn's work since pretty near the time I took an interest. I remember he being active on channel stuff. At that time I struggled to understand it and was negative about it since I didn't trust him. I failed to recognize some of the power and utility channels could have. I still don't know what Hearn's interest in them might have been. I suppose it's possible that it was one of the few of his interests which was not directed toward the destruction of Bitcoin.
For a long time I considered Gavin to be just a fairly naive clown who's heart was in the right place but who was pushing Bitcoin in the wrong direction and wasting resources, and I was happy that he seemed to be only marginally skilled and effective. Only after his meeting with the CFR and his secrecy around the event did I decide that he may also be actively working toward the destruction of Bitcoin. Whether there really was a shift at that point or whether I was mis-reading things earlier is unknown. But it doesn't matter much at this point. As you say, the appropriate position is at this point for both of them is 'don't bother'.