Let's not forget that they had faced this situation once before already - with all the misgivings brought up here!
In "Time Squared", the heroes know there's a disaster waiting for them somewhere ahead, and there, too, Riker says that there's no point in turning away from it. LaForge justly confronts him over the claim, and Riker, Picard and Worf all respond by apparently quoting a standing theory of some sort that says time loops cannot be broken. Which is doubly weird, as these three wouldn't seem to have a prayer of out-theorizing LaForge, or Data (who stays strangely quiet in the debate).
Well, the heroes did break the time loop there. So even if prevailing science supports Riker and Picard in "Cause and Effect", these very heroes should know that prevailing science is wrong...
As for the "turning back is a certain way to avoid the loop" argument, it's far from watertight. Starships often make strange twists and turns for this reason or that, and it's perfectly possible that a straight course ahead would have saved the E-D in this particular situation. Just plow straight on, and when a situation emerges where common sense says you should turn (say, there's an emergency call from port, or a safe route around a black hole starboard), you ignore it and keep the helm locked dead ahead. Hell, this is the very thing that saved the ship in "Time Squared"!
It's just that turning at that specific moment
should have been a good idea. After all, at that specific moment
(during the Observation Lounge debate), there was no obvious reason to turn, meaning a turn right then would definitely surprise Fate.
But would that be enough? Perhaps a starship acting perfectly normally would be safe, but a ship turning for any reason at any time would fall victim to the time loop. After all, time loops supposedly don't happen all that often - so, logically, maintaining a routine should keep you safe, while trying something uncommon would present a high risk of something uncommon happening to you.