You use "hung" when have, has, or had precedes it. In all cases, the past tense for hang is hanged. Most people are incorrect. Just because it has been accepted by the masses, who are extremely uneducated, it does not make it correct.

People got nervous using hanged because it reminded them of executions. That is why hung was used. It is not correct. It's such a shame that so many unqualified baboons are teaching naive people the incorrect word, acting as if they know something, when in reality they do not know anything. Please refrain from telling people "hung" is the past tense of hang. You are a disgrace.