I’m in my 30th year of dispatching. I worked for an agency that had 4-6 dispatchers on duty each shift. I currently work for an agency where there is only 1 dispatcher on duty each shift. In both agencies we dispatched PD, FD, and EMS.
I always maintain a professional atmosphere in the radio room. When I train a new dispatcher one of the first things I tell them is that all our phone lines and radio channels are recorded. I also let them know that, between private citizens and other agencies, many people may be listening to us. Keep background noise to a minimum, keep cellphones off (or on vibrate), and keep non-communication personnel traffic through the radio room to a minimum. Over my years of dispatching I really can't recall any issues that made either of the agencies I worked for sound bad.
That's not to say it was totally sterile on the air. We did have occasions to have fun in the radio room while working, and sometimes that fun made it to the air. However those episodes were brief and didn't happen on a regular basis. I don't know if the OP has dispatch experience but I think it is unfair to expect a dispatcher(s) to be totally cold and sterile sounding on the radio. I have heard unprofessional activity over the years, most notably on SPEN-1, but I think that that behavior is the exception, not the norm.