This is actually becoming a big deal. More and more "metrogyms" are specifically targeting "regular" guys and gals and some even deny membership to people of actual size or build apparently.
Now - for that grunting stuff. People do it. I do it. Sometimes it just a mind thing and helps me to push that last rep up. Other times, it because the f#&*in weight is heavy as hell, and it hurts! HOWEVER, there are guys that go in there and start grunting on their first rep, and do it loudly. THAT, pisses people off. I mean, the difference is noticeable to say the least. Kind of like the guy that comes in there half naked covered in Vaseline. The beach is 40 miles from here dickhead, and hows about buying some panties that actually fit...
Anyway, theres an etiquette I think, and most people follow it, some dont.