The GAA has rejected a request from Mayo to wear rainbow-coloured numbers on their jerseys.
The team sought permission from Croke Park to make the change for their 2023 National Football League games.
The move was taken in partnership with local mental health charity Mindspace, to show support for the LGBTQ+ community.
LGBT activist Sarah McDevitt told The Pat Kenny Show the rejection is confusing.
"While I do understand that organisations like the GAA have rules and uniforms, that is driven to make everyone look the same," she said.
"That's the whole point of uniforms and I understand that; however, I think the whole point is we're not all the same.
"In fact, some of us hide in the shadows because of fear and shame, and that's especially true in rural Ireland".
She said the organisation should want to include everyone.
"The important thing here is that visibility matters, and if you're not part of the LGBT+ community, you see a rainbow and you think, 'It's just colours'.
"The fact is it's not just colours - it represents representation and it indicates safety, and it indicates inclusion, and it might just save a life."
'Need to make brave decisions'
Sarah said 'gutsy' decisions need to be made around this.
"It's disappointing that the GAA have this particular attitude," she said.
"I think if the GAA talks about the GAA being for everyone, what's the concern?
"If they really want to be allies and take a gutsy decision to really support a group of people in rural Ireland, they can do other things".
'A chance to make a statement'
Asked what happens if other clubs feel they have to then follow suit, she said there is no harm in that.
"I think the GAA can talk all day long about how they're for everyone, but they need to make brave decisions to show that that's true," she said.
"They have a chance to really make a statement here that it is for everyone, and it is inclusive.
"If they want it to be the uniform, let everyone do it for particular games or a particular season, and show that inclusivity," she added.