[Melas]

No --- they don't need to ask individual guests their sexual orientation or religion or anything --- but when a group plans on some kind of event then why not allow people to see which groups have reservations?

Because no groups have reservations. Any group can just decided to show up at an amusment park.

[FITZ]

It's not like they're just deciding at the last minute to head on over to the amusement park --- and they're advertising the even so it seems that the park could notify families that September 18 is less than a family day at the park:

September 18 is the 9th Annual Gay Day at Six Flags Over Texas. This event has taken place for the last 8 years in a row and this is the 9th year.

Here groups can reserve picnic areas in amusement parks and other similar things --- that way they have their meeting area pre-arranged --- maybe this isn't quite the same but it sounds like it might be.