That is true, GPUs can handle much higher temps than CPUs but just letting it go could be damaging to the rest of his components. The problem might not be that the GPU has poor cooling, the problem could be that the case doesn't have good enough airflow and ALL of the components in the case are overheating. And like you said...CPUs are more heat sensitive so he should keep an eye on that too.
Rez, have you looked at your CPU temps yet? I am curious if they are going up too. Describe your case for us. How many fans do you have pulling in air? I wouldn't worry about AC, just take the door off your case or crack it open a bit when you play games and see where the temps level out too. My last system had a case with no intake fans so I just opened up the door when I played games to help air get in and out.
There are also PCI slot fans available that you can put in the slot under your video card if it is an airflow issue. They blow the hot air that comes off your video card out of your case. I am not sure how well it would work for you or if you have access to any but you can see in the links what I am talking about. They are a pretty cheap too.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835114024
http://www.newegg.com/Product/Product.aspx?Item=N82E16835888309