
I agree with the majority. The protesters intended to hijack one rhetorical situation--a military funeral--and introduce a second rhetorical situation in which state policy is the target. They did not silence or prevent the funeral. And while their speech act insults the mourners, the inflammatory signage is tactical first and foremost.
The policy under attack concerns gays serving in the military. The soldier being buried was not a homosexual. What if he had been? Could the protesters' intent to injure then be more easily argued?