I believe the morning is the go because your body will use what ever carbs are left first (as carbs are easy to break down to create energy. not usually many left in the morn) and then it will look for other sources. If doing hard cardio say over 60% of max heart rate then yes it will break down you muscle to supply a quick source of energy. But if you keep you heart rate below 60% max then due to your body only needing a slow release of energy to manage the work load then it will break down fat to supply the energy. I like keeping heart rate around 50-55% and I beleive 40-60mins is ideal in the morn. I think it is also good to do cardio for no more than 30 mins after your weight session once again below 60% H.R. (protein shake straight after). I only do cardio when wanting to get really lean otherwise I won't bother with it, personally I find it really boring. If I want to lose 1-2 kg then I will play with my deit by cutting the cabs down for a couple of weeks and this seems to work fine.
You are the master of your body, take control and sculpt it.