It is true that cars other than VW Beetles have engine fires but it is rare that those fires are caused by gasoline. The major cause is oil leakage and electrical shorts. Oil actually has a lower flash point than liquid gasoline. If gasoline drips on a hot exhaust manifold, it will simply evaporate. If oil drips on a hot manifold it will flash and set fire to any nearby grease and oily dirt.
All factory made cars that I am aware of have steel fuel lines. The VW is the only one that has rubber lines. It is the rubber line that deteriorates and allows fuel leakage. This leakage is always at one end or the other of the hose. The main problem is that the resultant leakage is near the distributor. Fuel vapor in the distributor WILL ignite and so will any nearby liquid fuel or fuel soaked fuel lines.
Now, with two fittings at the fuel pump and one at the carburetor, there are three possible weak spots. When you add a fuel filter somewhere in there you're adding two more week spots, for a total of five. In other words you chances of having a fuel fed fire with a fuel filter are 67% higher than without a filter.
One error that some have found out the hard way is that the fuel pump and carburetor fittings are 6mm. If you go down to the local auto parts store for a fuel line you're probably going to come away with a 1/4" hose and a few clamps. The 1/4" hose is close but is actually 6.35mm. This can be clamped down to 6mm but will eventually leak. Overclamping on a plastic filter nipple might not crack it outright but will induce stresses that may, over time, result in a crack and leakage.
Another problem is the pressed-in copper lines in the fuel pumps and carburetors. These have been known to pull out resulting in fuel being sprayed around. There is no way that the weight of a fuel filter, plastic or metal, is going to cause the line to pull out on the carburetor. It is simply heat cycle and vibration. If you're industrious enough it is a simple matter to convert to solid steel lines. Just yank out the copper lines, cut threads in the hole and install suitable fittings and lines.
I've never heard of a VW engine fire caused by an oil leak or an electrical short although I suppose some of you can (will) enlighten me. It is my considered opinion that ALL VW fires are caused by fuel leaks.
This is a bit rambling but the bottom line is that fuel leakage is, by far, the major cause of VW engine fires. You can tempt fate with a filter and rubber lines if you want - I don't really care, it's your car after all, but I'd rather err on the side of caution.