#IfMenHadPeriods, a feminist hashtag mocking what it would be like if males menstruated, has caused a huge storm on Twitter, with some labeling it as offensive towards transgender men.

“They’d brag about the size of their tampons” joked one user.

#IfMenHadPeriods they'd brag about the size of their tampons — Myka Fox Ⓜ️ (@MykaFox) September 6, 2016

“There would already be a law saying they could have a week off every month. #IfMenHadPeriods” joked another.

There would already be a law saying they could have a week off every month. #IfMenHadPeriods — Stargaryen 🌈 (@bitchwattafuck) September 6, 2016

A large and vocal group of people, however, did not find the hashtag humorous, citing transgendered males as the reason why the hashtag was both invalid and “offensive.”

“Ugh. Seriously. The #IfMenHadPeriods tag is vile. Trans men exist and DO have periods and cis women erasing them is not okay,” posted one user angrily.

Ugh. Seriously. The #IfMenHadPeriods tag is vile. Trans men exist and DO have periods and cis women erasing them is not okay — no name writer (@wordroot) September 6, 2016

Men have periods. If u only referring to cis men, say so. U are erasing trans men & trans masculine ppl who have periods #IfMenHadPeriods — Muting/Blocking = Self Care (@QueeringPsych) September 6, 2016

#IfMenHadPeriods is trending and I'm pissed off because I'm a man currently on my period and I feel like murdering everyone — Common Trans Boy (@TransBoyPosts) September 6, 2016

https://twitter.com/IKNOWTHATROAD/status/773155324274483200

“This tag is so cisnormative. Trans men can have periods. Menstruation is not gender exclusive,” claimed another.

#IfMenHadPeriods this tag is so cisnormative. Trans men can have periods. Menstruation is not gender exclusive — bella (@HS2KISSY) September 6, 2016

https://twitter.com/oddishkid/status/773211409958244353

#IfMenHadPeriods then it would be nothing new. men have periods all the time. trans people exist, i know, shocking! — @sweden (@sweden) September 6, 2016

#IfMenHadPeriods shows once again how very few people respect Trans folks, have any real knowledge of biology, or understand basic decency. — William Jamal Richardson (@DecolonialBlack) September 6, 2016

The founder of the hashtag, Jennifer Gunter, a female OB/GYN and self-described “sexpert,” has come under heated attack since starting the hashtag.

Gunter, who frequently tweets about periods, “patriarchal oppression,” and “mansplaining,” defended her hashtag, claiming that she “was tweeting in response to mansplaining about menstruation and mood.”

I was tweeting in response to mansplaining about menstruation and mood. https://t.co/FI8fqH5uru — Jennifer Gunter (@DrJenGunter) September 6, 2016

Fellow feminists and social justice warriors, however, are still posting in outrage at the hashtag and don’t appear to have forgiven Gunter yet.

Charlie Nash is a reporter for Breitbart Tech. You can follow him on Twitter @MrNashington or like his page at Facebook.