My take on it: Most LGBTQ+ rights issues are almost entirely settled and agreed on anyways at the greater societal level. You'd be hard pressed to find an appreciable amount of people that rationally want to take away normal, everyday rights from LGBTQ+ individuals. Sure there are exotic and controversial discussion points (E.g. child transitioning, odd bathroom laws, etc) but no normal business touches those issues with anything but a ten-foot pole and vague "messages of support". Brexit, on the other hand, is probably a 50-50 split within the overall population in terms of support and is an arguable/defendable position that rational people can and do make.
Meanwhile LGBT rights are pretty much universally agreed, and I don’t think that “LGBT support” is generally classed as a political view so much as an expected cultural norm (i.e. not showing support would elicit a severe backlash within the customer base).
