things like fusel alcohols which give the beer an unpleasant taste
The fusel alcohols and other unwanted byproducts primarily occur during the vigorous part of fermentation. The tiny amount of "fermentation" that's going on during bottle conditioning shouldn't generate those things. I'd go ahead and warm 'em up but, like someone else mentioned, keep it below temps that might actually kill the yeast. When I did it recently, the max they were warmed up to was 80-85 F. Carbed 'em up nicely, enough so that I went ahead and added them to my entries in the upcoming UMMO.