This is really technical, and pretty picky, and I really don't like applying my job to my pleasure, but I've got to comment.

My granddad used to have a saying "don't speak on what you don't know"....in this case, you are both guilty.

The guy is wrong because of his reasoning...it isn't exactly air currents that raise a bullet. That is a myth, very similar to the "bullet shedding myth", supposedly bullets sand themselves on the air as they fly because they are so fast, which is bogus. But I digress.

You are wrong because this actually CAN happen. It's called the magnus effect. Although I've never studied projectiles like bullets for this effect, I have studied the analogous scenario of a spinning rod (perpendicular to fluid flow) in a pipe of flowing fluids. If the pipe where stationary, two basically symmetrical "boundary layers" of static fluid would form on either side of the rod, in a fairly rapid flow, these layers detach in what is known as vortex shedding, which caused the failure of the Tacoma Narrows bridge in case you're curious....It's also why a flag whips back and forth in the wind.

However, if you start spinning the rod, these boundary layers become uneven, producing a velocity difference between the two "sides" of the rod, which creates a pressure difference similar to that of an airplane wing. So, this is VERY minimal in air because it is a low viscosity fluid (yes, it's a fluid, even if it isn't a liquid).

For example, if you're looking at the tail of your bullet in flight, and you have a strong wind left to right, and your bullet is rotating counter-clockwise as viewed from behind, this will induce a more rapid drop in your bullet...the same bullet in a right to left wind would raise.

It's a real thing given the right conditions. It wouldn't happen in still air, and it likely gets attributed to the wind any way if it were to be noticed on a windy day...the bullet drift horizontally with the wind would likely be much greater than the vertical drift caused by the magnus effect.

If I recall correctly, this myth honestly comes from civil war times. Soldiers would aim their cannons directly at the front line of soldiers coming at them, but the ball would "sail" over the first line and take out men in the second or third...which I would be prone to believing was an effect of their design, rather than the magnus effect.