The problem isn't that the sign itself is going to change anything for people, it's that it opens the door for more anti-trans laws. Every law that passes to restrict the rights of LGBT folks, women, and any other minority or oppressed group only takes us one step further in the wrong direction, and eventually we run the risk of those steps taking us back to a place where some people are no longer safe, or have to watch their basic human rights slip away. You might say it's impossible to go that far, but we only think that because it hasn't happened yet. Yes it might never happen, but is it worth the risk? Why just accept legislation that further marginalizes people, legislation that brings to power a narrative of otherness and disrespect for their wellbeing? This law may not effect you now, but other laws that this paves the way for certainly might, or they might effect other individuals or communities that you care about.