AIO My managers think customers shouldn't be "forced" to see anything LGBTQ in the store

Hello all, I am a transgender man and a supervisor in retail. Specifically, retail in a 21+ store. Behind the counter, we have several 8.5 x 11 whiteboards for our cashiers to write things like "Staff favorites" or "Daily promotions", with their personal picks for the day, their favorite products, things like that. Yesterday, one my employees, a transgender woman, wrote, "Trans-scending Deals!" at the top of the whiteboard in pink and blue, with that day's promotions, and her favorite items, written with drawings all over the rest of the whiteboard. The title was smaller than the rest of the text on the board, and the word "trans" was the only thing written in pink and blue.

About an hour later, I noticed her erasing that one section at the top of the whiteboard before putting it back in front of her register. When I asked her why, she said "Because I was told to." I asked my fellow managers if there was something wrong with it, to which I was told quietly a few reasons. Those reasons were, "We don't want to invite any negative energy into the store. We want anyone who comes in to feel uncomfortable and not offend anyone, and we don't want customers thinking that the company promotes that." Now, we live in a fairly liberal state in the US. These reasons really bothered me. If their reasoning had been, "We don't want customers potentially harassing or hurting [employee]", I could've gotten behind that. But the reasons I was given sounded a bit transphobic. I then shot my store managers a quick DM, explaining what happened, what was said, and how it made me uncomfortable. I explained that the reasoning came from transphobic rhetoric, rather than from protecting the employee. Well, my general manager then pulled me into the office with the offending manager to have a talk. The phrasing used was, "Lets talk about your rant," which I can't lie, irritated me.

My GM then proceeded to tell me that she agreed with the manager. I basically reiterated what I had said in the message; that the reasoning was transphobic and that if the reason had been for protection, that would have been a way better excuse. The other manager apologized for her "poor phrasing", which I forgave, but then my GM began justifying the original reasons. She said things like, "If we let [employee] write trans or gay stuff on the whiteboard, we'd have to let [other employee] whatever stupid shit he wants on the whiteboards. We'd have to allow them to write religious or conservative ideology on their whiteboards (which I don't know why those are comparable?) We need to keep politics out of the store. The company is very supportive, but we need to maintain the appearance of being neutral; we won't be actively supporting either side. Any customer that walks in needs to feel comfortable and non-offended. Those whiteboards are for staff picks and promotions only (which is exactly what [employee] had been using it for?).

I then asked why it was acceptable for us to have pride flags decorating the sales floor last June, to which she responded, "Well because that's pride month, and were celebrating then." At this point I stopped responding, as it seemed the conversation was going nowhere, and our GM is notorious for talking over people's perspectives in favor of her own (I would like to note that both of these managers are cisgender). If just felt like 20 minutes of being talked down to by people who do not understand, if I'm completely honest.

Now, the employee and I are considering having another conversation about the subject, and potentially starting an LGBTQ advocacy group in-store, as neither of us were okay with the answers given, and some of the other queer employees have been rallying around us, too. I would like to hear other perspectives on the matter, as I'm not always great at formulating my responses, but mostly, AIO?

TLDR; My manager thinks that we should not be openly showing or supporting LGBTQ ideas in the workplace.

Edit: Would like to clarify that I do not work at a sex shop, but a store where anyone under the age of 21 are not allowed inside.