Emet-Selch was almost certainly telling the truth. His primary concern was to ensure that his people were seen as actual people and that their history and culture was brought back/preserved. His name also roughly translates to 'Bringer of Truth'.
Hydaelyn, meanwhile, has been anything but open and honest. She has lied repeatedly - both directly and indirectly.
Characters have been killed off for far lesser reasoning. I think it's about time we apply the same standards across the board if we can find a way to safely extract her without shattering reality further.
There can be no mercy for false deities.