Except that they didn't. There were quite robust rebuttals, which were just not reported.

I saw and heard them rebutted on the media all the time.
Question Time, Any Questions, News Night, Andrew Mar, the various leaders' debates.........

I am sure that Guardian and Mirror editorials and reports did the same.
It was also a major issue in the 2010 election.

It was a fair fight, and in England the Left lost this time.
You can not ascribe that result to a feeble minded electorate or to a feeble Left incapable of responding to the opposing campaign.