Atheist groups like the Freedom From Religion Foundation just cannot keep their noses out of other people's business. It doesn't matter if school administrators, parents, and students are fine with students praying before football games the Christian flag gracing the school flagpole. FFRF makes it their business.
There are some people who are so committed to sanitizing our country of any influence of Christianity they don't even care if they dishonor the dead in doing so.
At the time, the Created Equal team was on public property and had earlier confirmed with local police that they were free to set up their signs there. In spite of this, the school resource officer insisted they remove their signs and when the team refused, he began taking them down himself, seemingly to confiscate them.