Most AC units have a filter so the air is rather clean. Just keep the filter clean and the air will stay clean and the AC unit will work better. I think the additional cooling and air circulation is a benefit if anything as well.
What might be an issue is the cycling of the compressor in the AC unit. Every house is wired different but in mine when the AC cycles my screen will flicker slightly and I will get a slight click sound from the speakers. I figure during our short summers the harm could be minimal but over a period of years it might cause a problem with the power supply. This is my only concern about running my AC while watching TV. If I don't though it quickly warms up into the 80's in my house and I figure this is more harmfull to the TV.