Telling a chess player that chess is a silly game with a hodge-podge of rules crudely kludged together can be described as offending. It is a bit crass but to each their own.

The kind of communication I want people to be arrested for is way beyond that level which I would describe as “offending”.

But assuming you are asking in good faith: Why do I want people arrested for intentionally sending distressing pictures? Same reason I want anyone arrested for punching someone in the face. Because I think that behaviour should not be tolerated in civilised society and I want it to happen less often.