The Boy Scouts often use public facilities.
Besides, IMO this seems more like a free speech than a freedom of association issue.
Read the first two paragraphs again:
Philadelphia homosexual activists say they will seek a court to prevent protesters from attending their "pride" events in the future.
But organizers from Repent America, a Philadelphia-based Christian organization, say they will attend the events, even if it means defying a court order and getting arrested.
This isn't about standing across the street from the venue and protesting - if the gays were fighting that, then I would be on the side of the protestors. However, the anti-gay group wants to into the event, whether they are invited or not. Freedom of association.
There has been no such court order - the protest spokesperson was engaging in hyperbole.
Sounds like the mayor is on the protestors side, as well.
AFAIK, "attending" the event meant last year (and likely means this year) standing on a sidewalk during the event. The event is held - again, IIRC - on the public street. It looks more like a free speech and freedom of assembly issue than a freedom of association.
Anyway, if homosexuals are going to be given public money, all gloves are off.