There's a world of difference between individual fans doing so on an unofficial or casual basis, and a club and it's officials doing so on a formal basis.
Similar to the way if you've ever worked a job involving customers or clients you might get an obnoxious customer (rude, nasty, demeaning, etc...), and when you're dealt with them you might turn to a colleague (away from other customers), and say, "what an idiot they were" (or other words that express a similar sentiment).
But the company/organisation/business themselves sending a letter on letter-headed paper to the customer in question saying, "piss off fishface, you're a t**t" would be a whole world of difference.