It isn't surprising that this hatred was allowed in a government building... My surprise that someone spoke out against it.
That is actually pretty tame by fundamentalist standards. I can assure you he toned it down for public consumption, compared to what he utters from the pulpit.
I'm not saying that to justify it, just to put it in perspective. This is just matter of fact dogma to fundamentalists; they don't see it as hateful or otherizing; indeed, they even see it as "loving" in that they are warning sinners of the peril they put themselves in. And I would imagine that the ironically named Rev Snipes would be baffled and hurt by the pushback, for about 5 seconds, and then proud that he had been "persecuted for righteousness' sake". In the world of self-ratifying nonsense that is fundamentalism, he would see the criticism as confirmation he's doing it RIGHT.
Why not more people calling him out? They realize they may jeopardize their own hold on power with such call-outs as they will offend way more people than they will give pause. The political solution is, as AOC puts it well, not to focus on "calling people out" but rather on "calling people in". They need to speak to the kinds of invocations they want to see rather than the ones they don't. And even these two objectors did a good deal of that. After all, if you're arguing FOR inclusiveness and ecumenical sentiment, that is something that even a fundamentalist will understand even if they think it's misguided. But if you directly attack them then they'll just see it as an existential threat. It should be framed as a disagreement about what's appropriate, not over opposition to what believers believe.
When you stop to think of it, that'd just be good politics, as you don't want to commit the opposite error in the other direction. In other words if Rev Snipes made the error of turning what was supposed to be an inspirational leadership moment into a thinly veiled ideological attack, it makes zero sense to respond with an opposing ideological attack; then it's just two ideologies arguing about who is right. It needs to be acting not in accordance with ideology but in accordance with what constitutes civil debate and discourse, regardless of the view that informs it.