Oh well, there has to be one in every crowd, I guess ...
My dogs have always known when they got haircuts. Even my German Shepherd knew if he got shaved down, and would hide down the wall, stick his head around the corner, and bark at the door. He knew he looked funny. OTOH, my little 3-legged doggie ALSO knew when she got a haircut, and would prance around in circles in front of anyone who'd stop long enough to tell her how *beaUtiful* she looked. Same with the Westie.
Now, Puddie's a cotton coat, and he could care less if his hair is cut, other than when it's short, he feels like velvet, so he gets rubbed a lot more (which he dearly loves). Bella's coat is long and has always been long, but she's a proud little thing, and I think she'd know if she got cut too short.
That being said, their reactions only last a few days, then they fall back into normal routine, whatever that is.
Puddie is "substantial"; he's a little tank. Short hair on him looks good. Bella's a dainty little waif; if she was cut as short as Puddie, it would look like we were starving her. She looks good in a long coat.
The only thing I can tell you is that the pup will get over it in a few days, one way or the other. And if he looks funny, lavish him with attention and take his mind off it. The other thing to remember: if you hate it, it DOES grow back. And this time, maybe you can brush him every day as it grows in, and he won't notice when it gets long again