Bob Crow's article demands a fuller reply which I don't have time to write but I posted this response to it on an RMT Facebook page.
The article which is linked from the text “movements in other countries that are critical of the EU are led by the left” shows no such thing. In 4 out of the 6 EU countries specifically mentioned there is no indication of which side is the critical one. Of the remaining 2 countries: in France it mentions 2 parties being critical, one from the left and one from the right; in Germany it mentions a right wing party. I guess that article was linked to defend against accusations that anti-EUism is a right wing policy. That accusation still stands.
In the recent local council elections UKIP (a right wing party critical of the EU) got ten times as many votes as TUSC (a left wing party critical of the EU). In Eastleigh that figure was 185 times. We should criticise and fight EU policies when they act against the workers but we should also understand that paying too much attention to the EU will help the right much more than the left if it helps us at all.