How to tell my instructor to increase glidespeed with headwind?

Nik wrote:
Ok, my instructor did a simulated engine failure in the pattern; winds
were around 20kts in the air and 13kts on the ground. Did everything
perfectly; however after we took off again, he told me to maintain 65
kts next time, and I totally disagreed.
The manual says 65 kts for best glide speed; however that is in calm
air. As a glider person, I know adding about 1/2 the headwind component
will give the greatest distance.
After the flight I pulled up the Glider Flying handbook online and it
says:

"...it is apparent that flying a faster airspeed as the headwind
increases will result in the greatest distance over the
ground. If this is done for the polar curves from many
gliders, a general rule of thumb is found, namely, add
half the headwind component to the best L/D for the
maximum distance."

But even after telling him that he said that doesn't apply to power
planes, also saying that manuals never give best glide, and there has
to be a reason for that.

Do you guys have any ideas on how I can really convince him? Any good
sources?

Thanks!
-Nik


Most airplane training books don't discuss this concept, and POH rarely
ever mention this. We are taught by a system that enforces the view
that we should follow the POH exactly and not improvise anything. So it
is not unreasonable that this instructor never gave much thought to
this concept until you challenged him. However, most intelligent people
will realize this as soon as you point it out. You owe him at least
that much. If he doesn't turn around, then you have to start wondering
what other uncorrected misconceptions that he is passing on to you.

Everyone makes and has misconceptions, but stubbornly holding on to
them in the face of opposing evidence is what distinguishes an
intellect from others.