Just because somebody yells bad things and does word fighting a lot doesn't mean they do illegal things. Growing up, there was a family that lived near me that yelled, screamed, and fought a lot every day and twice on Sunday. Many a time, I thought the mom was dying; yet, she never seemed to have so much as a scratch on her. To hear them holler, you’d never guess that they were extremely honest (and had friends in high places).
If these people that you are writing about really are bad news, the police already know about them and are probably watching them anyway.
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To help you think twice about this, here's a true story that happened to a couple married acquaintances of mine. (Dick and Jane are not their real names.):
Jane took a trip to Vermont for a couple weeks. While Jane was gone, Dick bought a new table saw. Excited about his new saw, he decided to try cutting up a bunch of wood. The saw was a bit noisy; so, out of consideration of his neighbors, he worked in his garage with all the doors closed, cutting all the wood.
That same evening, Dick cleaned up himself and the house and went out to dinner and then to pick up his wife from the airport. Around midnight, when Dick and Jane got home, they found that their home was surrounded by police cars and the road was blocked off. Dick stopped at the road block and asked what was going on. The policeman asked if he was Dick X... and he said, 'Yes, I live at .....'
I won't go into details on the rest; but, suffice it to say that if his wife hadn't been with him, Dick would have been in big trouble. The neighbor thought Dick had killed Jane; and, when he was cutting up wood behind the garage's closed doors, imagined Dick was cutting up Jane's body to dispose of it. So, she called the police and told them so.
…The neighbor is still in trouble, both with Dick and Jane and with the police!