The father took reasonable steps to ensure his son didn't disturb others by using a private stall and keeping the volume low. The woman's aggressive behavior, barging into the stall, was a gross overreaction and a violation of privacy. The pool staff even confirmed that their main concern was recording, which the father was not doing.
While the father claims to be considerate, his actions created a potentially uncomfortable environment. Using a phone in a changing area, regardless of privacy, can make others uneasy, especially given widespread concerns about surreptitious filming. The woman's reaction, though forceful, stemmed from a legitimate concern for privacy and safety in a shared space.
The father showed some consideration by using a private stall and keeping the volume low, but he should have been more aware of the general discomfort phones can cause in changing areas. The woman's approach was excessively confrontational and violated the father's privacy by opening the curtain. Pool rules should be clearer about phone use, but basic respect for others' personal space is also essential. Ultimately, the woman should have handled the situation with more tact. The father's actions were not malicious, but the woman's aggressive confrontation was unwarranted.