don’t get me wrong: I absolutely LOVE an ice-cold light american lager, or standard american lager (Blue light, Genny Lite, PBR, High Life, etc.), but to the above-point, that can really take away from a lot of beers. So yes, a frosted mug will absolutely mask and distort the flavors of a beer.
The short answer: drink your beer the way you want it. However, I would encourage you to do the following: Pick up a 6-er of Sierra Nevada Pale ale, or something relatively hoppy that you can get in your area, the same with a stout ,the same with a decent lager/pils (warsteiner, radeberger, victory prima pils), and try all of them in a frosted mug, then each of them at around 45 degrees (just take them out of the fridge about 10 minutes before you drink).
At the right temperature, bitter hop-forward beer stops tasting like just bitterness and starts tasting like citrus and pine, stouts start tasting malty and roasty, pilsners start tasting nuanced and complex, along with the crispness they would typically have at sub-arctic temps.