No one here is defending the heter.
We're defending the honor of Talmidei Chachamim.
Good that you cleared that up.
There seems to be some sort of disconnect.
If someone says "your Rebbi messed up big time"
to which you respond "how dare you disrespect my Rebbi!?",
It comes off as defending your rebbi of the mistake.
When really it's simply, "yes, my Rebbi made a mistake, but that doesn't mean you can start disrespecting him."
That is fine and admirable with me, but its better to be clear.
Because some here are still not sure if their Rebbi made a mistake, and will attack anyone who says so.
I think that anyone who is affected by this mistake (and personally I think everyone is affected) should make it clear to the world that there was a mistake. That bitul kidushin is not something taken lightly.
Though that still doesn't absolve them from further attacks either.