This is one of those things where I beleive the danger is overstated. And I think that can be proved by the multiple millions of safe fuelings that happen every day all over the country.
The signs and the fear tactics are all necessary to inoculate the station and the fuel company from lawsuit in case there is a rare occurrence. Interestingly most gas station fires are short, non explosive and quickly contained.
The only real danger I see to people with RV refrigerators is in the event of a large spill at a station, which is very unusual. All gas station hoses have break-aways links that immediately shut off the flow of fuel in case someone drives off with the hose still in their car...this happens quite frequently with virtually no dire consequences.
I think statistically your chances of a fire at a station because of your refrig. flame is about the same as being in an Airline crash.
Gas stations are very well ventilated and often windy/breezy not conducive to explosions.
Additionally I have stopped at least three times at cars engulfed in flames along the side of the road to assist the passengers. I waited patiently for the car to explode...it never did. One time I asked the firefighters who responded about this and they told me they almost never explode. And thats with the whole car on fire???
No I think common sense and real world experience tells us this is far safer than getting back on the road from the gas station.