Hate groups (such as the KKK) are allowed to hold rallies in public parks. What amendment is this? and what is the right/freedom?

In 2016, two-year-old lane graves was wading in the lagoon of an orlando walt disney world resort and watching a family outdoor movie, when an alligator snatched the boy and disappeared. the resort had signs which read "no swimming, deep drop off" posted along the beach area where lane was taken, and his parents were a few feet away when the incident occurred. several hours later, lane's body was discovered about 15 yards from where he was taken by the gator. a disney employee said this was not the first time an alligator had been spotted in the lagoon beach area. if the graves family files a lawsuit against the resort, what theory would best support their claim?