This whole Dennis Skinner dinosaur nonsense just serves to highlight the double standards of those on the left. As has been pointed out elsewhere, it's perfectly fine to denigrate Baroness Thatcher and look forward to her death so you can have a good party, but a relatively innocuous comment about Dennis Skinner by the Prime Minister is met with typical faux indignation.
In any case, Dennis Skinner is perfectly capable of dishing it out - just check his Wikipedia entry - so I'm sure he's capable of taking it and doesn't need any help from a bunch of humourless whiners.
No, it's just typical double standards - they seek offence where none is intended. Grow up.