Seymour told RNZ the T-shirt was not sexist, and was about the "idolisation of meat".
"It is a club of people who idolise meat, and produce pictures of athletic people, men and women, with cows' heads on them."
When asked if the T-shirt was sexist he said, "No more than a sexualised man to meat".
However, he said he should have worn the male version.
"Maybe I should have worn the male one, I don't know."
Seymour took issue with the scale of the reaction, and said it would be a very "sterile world" if politicians were unable to take photos with students on campuses.
"It is rather a shame that our state broadcaster thinks this is the big issue.
"I would much rather be here talking about the closure of charter schools."