I'll add my voice to say that the instructor is disregarding the important fundamental of providing as much reaction time as possible during the learning process. Everyone recalls their first flight where they were exhausted in the first five minutes.... because in part we got mentally overloaded. More reaction time lowers the mental load and eases the learning process.
I'd pull the throttle back and find my comfort zone and trim the plane for level flight at that speed. If the instructor objected, I'd find another.
The other issue is that likely the instructor is trimming the plane for full power and as others have noted, trainer planes normally climb at full power. This means that when reducing power, the plane is out of trim and will tend to dive for the runway rather than displaying a good landing glide path and will make landing a lot harder (emphasis) than it needs to be. No old hat pilot wants to land a plane that doesn't establish a proper landing glide path because having to deal with pitch when added to keeping the wings level, alignment with runway, and proper throttle for correct air speed soon present mental overload to even many seasoned pilots.
An example of overload. I recently completed a Yak that was out of trim between even mid range power and power off. Combined with that, the throttle was far too sensitive in the low power range where a narrow band of power was needed to keep the prop from braking the plane too much but keep air speed proper for landing. It was a challenge to land because it overtaxed me. Add a gust of cross wind on the large vertical stab to induce sudden roll close to the ground, and it was tough.
After getting the plane in trim for power on/off flight and reducing the throttle stick sensitivity in the low power zone, life got so much better and landings are enjoyed instead of feared.
You got into this hobby probably to enjoy flight.... not fear it. My bet is that if you speak frankly to the instructor about this and ask him to trim the plane for a slower speed... he will comply.