No, they should do the most soft Brexit possible. Cancelling the referendum result altogether would be wrong.
Hard Brexit is what was sold by the Leave camp, with the exception of a few idealists like Daniel Hannan and careerists like Johnson. It should be a hard Brexit. And the EU will deserve the consequences too as its as much a failure of our system as a general culture of ignorance about the EU institutions in the UK.
The people didn't vote for Hard Brexit - they just voted for a vague concept of Brexit. The most sensible option in that spectrum is the one Parliament ought to pick.