I just finished a i7 build in my full tower haf 932 (had a dead psu at first)
Being my first build with cable management behind the case, i went a little crazy and tried to stuff everything back there. It so happens that i had to use electrical tape to tape some of the 4 pin case fan molexs flat against the metal chassis. In addition, it was still a little squeeze to get the panel on, but it fit.
My parents were kind of worried that the metal chassis (where the mobo standoffs are placed) would get extremely hot and possibly melt the wires + short my system.
Is this actually a real + justified concern? To me, it seems that the case fan wires with the 4 pin molexs were hardest to fit in the back, and i just assumed its fine for them to be pressed (in my case, electrical taped) to the chassis with no problem.
In general no, the case will stay quite cool, wire insulation generally melts at a temperature well above boiling point. If you need to convince them, remember metal conducts heat as well as electricity, so for one part of the case to get hot enough to melt the wires the whole case would have to be hot enough to melt wires, and since the wires melt after water(and flesh) boil, have them touch the back of the case, no burns then there will be no issues with wires melting.