Dear friend, I feel bad but I think you are mistaken. RM is using a very sinister legend story called Pied Piper of Hamelin for this song which is why it is called Pied Piper. Please go to Wikipedia and read the plot of this story - the Piper plays the flute to lure children away from the village he is exerting revenge on and they were then put away in caves. Another version is they were all drowned in the end. Yet another one suggest they only released them when the town paid him a lot of money.
Incidentally, there are many songs with that title, including a Christian song that tells the spiritual harm Pied Piper does to the mass as leading them astray, exchanging God's truth as lies and lying :
http://www.metrolyrics.com/pied-piper-lyrics-petra.html
Meanwhile, BTS's lyrics are clear near the end the song that they are musicians luring children with their flutes (what PP does), saying:
"I'm taking over you"
"You will never get out of this. Never."
"I am ruining you, will you forgive me?"
All of this is very creepy, almost like sexual aggression and blatantly telling their victims: we are here to control you and make you obey us. We are sorry but we will ruin you for our interest! I suspect they are actually casting spells and exerting mind control over the audience in plain sight!