This was a gag line for the manzai duo ツービート.
If everyone does something (even if they aren't supposed to), it's ok.
Examples found on the internet: 皆でコスれば怖くない？！  If everyone does Cosplay, there isn't anything to fear.
みんなで太れば怖くない If everyone gets fat, it isn't bad.
合唱は皆で歌えば怖くない  If everyone sings in a chorus, it isn't scary.
ツービート was made up of: ビートたけし (Real Name: 北野武 きたの たけし) ビートきよし（Real Name: 兼子二郎 かねこ じろう）