I refer you to my post above that referred to what his actual position was.
He said there were a lot of things wrong with the EU (which there are), that he would seek reforms based on what he saw wrong with it (which he would have), but that blaming immigrants was nonsense because there are no restrictions we could put on EU migration whilst in the single market (which is correct), that it would be daft to anyway whilst a single market exists (also correct, look at what has happened in the US), and that the problems immigration causes can only be tackled by greater investment in those areas of the country experiencing problems (which is obvious) and by paying people fairly (again, obvious).
The PLP and its hangers on are criticizing him because he did not lie to the electorate. If that means he isn't credible, then I don't want a credible leader.