BS”D
If we do something RIGHT and someone snitches because he is ASHAMED of what we are doing, and the powers that be find a way to close it down, then that is mesira and the person who snitches is who we think of in velamalshenim.
That psak is not a blanket psak either. We don’t go snitching because we see something wrong. Maybe in the case of a D-ek where if he had been stopped his investors would not have lost hundreds of millions of dollars and he would not have become a true moiser who ENTRAPPED people into breaking the law, there is no mesira. Maybe in the case of a Ponzi scammer there is no mesira. Definitely in the case of a Schein trespassing on private property to film kaporos in a way that causes damage including anti-Semitism there is no mesira to call the cops and get him booked for trespass. In any case a shyla must be asked even if it is an abuser who is being reported.
But to just go and report a violation for the sake of doing so, where there is nothing halachically wrong except MAYBE dina demalchusa dina as someone decides he sees it? And thereby causing financial damage to a Yid who is not causing real damage to anyone else? If any rav claims that is not mesira, then he is a rav who should be paskening only after the latest time for Mincha.