Since when is it the voter's job to 'be kind' when a politician cocks up? Or forgive them when they lie? 
It is the politicians' job to work in our interests, not their own, and to tell the truth if caught out. And resign if found to be lying.
Fuck this idea that poor ickle Dom is being picked on.
If he cocks up and lies about it, he needs to go - the same as Ferguson was made to go and the Scottish Health advisor woman.
If you are responsible for setting the policy and can't keep to your own policy, you need to resign.
End of.