Mike Baird's decision to back down on his government's historic ban of greyhound racing was being pilloried online, even before he formally announced the about-face.

Hundreds of negative comments poured onto the Premier's Facebook page on Tuesday morning, as news of his reversal on the ban filtered out ahead of the Premier's press conference.

"You are gutless," said Facebook user Nick James.

"Spineless," opined Nick Calver.

Mr Baird's moral convictions and his use of Facebook have both been integral to the Premier's image.

The Premier has invested heavily in his social media image, paying digital "guru" Tony Story tens of thousands of dollars for advice before bringing him on staff as head of digital media.

But on Tuesday the reaction was universally negative and with references to the Premier's repeated previous refusals to change course on the policy.

Mr Baird's most recent Facebook post - celebrating Taronga Zoo's 100th birthday last week - has become a forum for people to express their fury about the reversal.

"When push comes to shove, self-interest always kicks in with politicians," said Facebook user Sylvia Massara.

Animal rights groups were also criticising the Premier. He had appeared alongside the RSPCA when announcing the ban, for which he won international praise from animal rights organisations.

"The politicians who pressured Premier Baird to overturn this ban are set to have sleepless nights," said former police detective Lyn White from Animals Australia, the group that helped compile material for the Four Corners expose that set the ban in motion.

"Their political destinies are now wedded to an industry whose sense of right and wrong went missing decades ago."

Fairfax Media revealed this week that investigations into greyhound mass graves are ongoing.

A previous mass grave was also handled by the Premier on Facebook, after it was revealed 99 greyhounds had met a brutal end in the Hunter Valley.

"Our worst fears have been realised," Mr Baird posted. "Ending this cruelty is simply the right thing to do."

Even Kristina Photios, a senior staffer at Liberal-aligned lobbying firm Premier State and the wife of party powerbroker Michael took to her personal Facebook to disparage the Premier's reversal: "Apparently shock jocks run the State, so why do we have these expensive middle-men?

"You will be slammed if you do, and slammed if you don't. So you might as well be true to your principles and at least keep your integrity."