Even using such a thing as a case fan connected to your mother board is a very bad deal but at least they have stuff in there to minimize all the electrical disturbances caused by inductance and such. To see the effect of this, turn on your ceiling fan and touch the ground wire not connected to anything, (Not he line carrying the current + positive live wire which can kill you), the inductance feedback will give you a shock just as bad.
An LED light does not cause thsi problem bt a tube light definetely will. Why not just get a rs 200 adapter and hook it up to that? Same with the case/CPU fans.