After a little bit of this rubbish, I would simply inform him that I will drive at a safe, reasonable and prudent speed. This means always assuming that there could be an accident around the corner, or that there could be heavy traffic. As your driver instructor probably says, you need to be able to stop in the distance you can see ahead. This is reasonable and prudent. You also need to drive slowly enough to react to anything you can reasonably expect (animals jumping into the road, children playing, cars going through red lights, heavy traffic ahead, etc.)
However, aside this, you can and should speed up when you see everything is fine. If you can see 2 km ahead of you, and it is clear, you are stupid to slow down to 30 km/h for an imaginary danger. On a straight road where you can see there is no bad spot, your safe, reasonable, and prudent speed could be 130 km/h--or even higher, if you are on a freeway and it's all clear. Around corners, you might have to slow down to 80-100 km/h, depending on the line of sight around that corner. If you get too many false alarms about danger, it makes sense to disregard them and pay attention to the road instead.
Or, if you have a smart phone and 3- or 4G connection, get real time information about the route you are on. This requires pulling off the road and stopping before texting, but once you get real-time information, you can find out about the accident that isn't there, the fallen rocks that are long gone, or the slippery roads that were long since cleared up. And if your back-seat driver doesn't like it, he can get out and walk.
The same for the Washtowel. They kept claiming that the end was upcoming. They had us slowing down to 30 km/h when 180 would have been reasonable and prudent. You get to the next bend, they claim it's there and you need to really slow down (80 km/h would have been plenty). They kept claiming the end was upcoming--in the late 1980s, 1994, before the end of 1995, 2000, 2001, after September 11 2001, toward the end of 2006, and ongoing. After too much of that rubbish, I decided that I would proceed at a "reasonable and prudent speed". True, September 11 was difficult--still I managed to get around that "danger" at "80 km/h" without any hardships. And I could take the 2006 at "130 km/h" without incident.
Additionally, this makes heeding a real hazard more unreliable. The danger is that you get complacent that this is another false alarm or that you pay too much attention to the false alarms that you fail to note the real problem. They harp so much on pious-sneering and attending all the boasting sessions that you are distracted from the real threat of excessive debt. So you "slow down" by pious-sneering and cutting back on regular work, all the while you are "texting while driving" by doing this. You then prepare for the problem that isn't there, only to run into the debt tree that you were distracted from. Not to mention that they create a "hazard"--excessive donations, wasting money on Grand Boasting Sessions, cutting back on secular work so you can pious-sneer, wasting gas and resources on pious-sneering, and not being able to invest in silver or gold (or anything else that might be worth it when the inflation tree or the debt tree come up) all prevent you from negotiating the actual hazards. Here, again you need to pay attention to the road (that is, the world itself) rather than a religion that is there to give false alarms.
