Actually, on a fractional rig, it can be more dangerous, since the mast may not be supported at the point the forestay attaches to the mast. With a masthead rig, the backstay and forestay attach at roughly the same point on the mast and will oppose each other. As long as the rigging is in good shape, it really shouldn't matter much with either type of rig. The larger forces generated by a masthead rig's larger sail are offset by the fact that the fractional rig may lead to the mast pumping.
SD, you're kidding, right? On every fractional rig I've even seen (including our own) the side-stays connect at the same point as the forestay.
Granted, the angle might not be as great as from the top of the mast to the back of the boat (a backstay) which is an optional extra on our rig, but I cannot see how you can say it "may not be supported".