This sort of reminds me of this Photoshop course I was taking a while back. In one class, the instructor was teaching us how to swap heads in engagement photos. It is a little known fact that when you are shooting engagement photos with a digital camera, it is impossible to take a photo where both of the persons have their eyes open. So what you have to do is take a bunch of photos and then swap the head of say the guy with his eyes closed with the head of the guy with his eyes open from another photo. Sure, it is an egregious sin akin to condoning slavery, but if you want to make a living as an engagement photo photographer, you just have to man up and do it. Nobody is going to buy an engagement photo if one of the persons in it has their eyes closed. Either that or you have to shoot film because the problem never arose back when photographers shot film. This is what I mean about the need to remain flexible on these issues.
Your instructor seems to be of the "those who can't do, teach" school. Most digital cameras, as well as later film cameras, allow you to take multiple shots in rapid sequence.. You are bound to get lucky on a least one of them
I am not a photojournalist or documentarian, and have no qualms about digitally manipulating my images. My scanning workflow involves having my scanner software automatically open the images in PhotoShop where I can remove dust and scratches, adjust the levels control and reduce to 8 bits per channel and save the image. I then open in Lightroom and make further adjustments (since Lightroom doesn't change the original file). On one occasion I have merged two images into one for a large family portrait, but rarely do that.
I mostly use photoshop to correct scanner limitations and issues with the goal of making the images not look photoshopped. I believe that I am a better judge of how an image should look than the scanner manufacturers, scanner driver authors, and scanner software authors: decisions are being made for me at every step, and it requires PhotoShop to correct these.
When I shoot color, I usually use Velvia 50. The world is not as bright and happy a place as it appears on Velvia. I grew up shooting that film about which we generally don't talk, but about which Paul Simon sang:
"Kodachrome
They give us those nice bright colors
Give us the greens of summers
Makes you think all the world's a sunny day, oh yeah"
The point of that song, as far as I can tell, is that our memories, and the photographs with which we support them, although authentic and "real" do not necessarily represent "reality".
My photographs, although generally not "doctored" do not really represent a documentary of my life.
I take photographs at weddings, but not at funerals.
I photograph street performers, not the homeless.
My albums are full of happy memories, not painful events.