Is Grant saying the unions are homophobic?

1 News reports:

Labour MP Grant Robertson says being gay was “a factor” — though not the entire reason — behind his unsuccessful runs at his party’s leadership in the mid-2010s.

The outgoing MP put his name forward for the Labour leadership in 2013 and 2014 and was narrowly defeated. While he had won the majority of support from his caucus colleagues both times, he lost once other votes from the wider party membership and union affiliates were counted.

In 2013 Grant only got 17% of the union vote. In 2014 he only got 19% of the union vote (and would have won if it were not for them). So one can only assume that he is saying the unions are homophobic.