The two things aren't divorced from each other. Figures on the extremes have a negative view because an impartial organisation
I'll let
@Tom defend his own points, but specifically on this one ... according to Dimbleby's book, the panel booking process is by party, rather than by individual. Therefore it seemingly wasn't the case that pro-European MEPs chose not to appear, it would be that the Westminster parties would put forward a Westminster representative, rather than a European one - at least in part.
A strategic error, perhaps.