As a pilot that does a lot of commuting to and from base, here's my two cents:
Check-in crew, gate crew and cabin crew are well within their right to decline oversized or heavy bags to be brought onboard, especially with a full airplane.
While it might be embarrassing to tell customers they can't bring all their gear, what you are in fact doing is providing a service to the rest of the passengers who are indeed aware of the regulations and adhere to them.
When someone else is allowed to board with 2-3 pcs of hand baggage, which leaves me with only underseat storage for my cabin-sized bag (or even smaller backpack, depending on a/c type), I believe the only appropriate thing is to enforce the rules. No one likes to get a speeding ticket either, but I think the general public is happy that there are measures in place to take out the bullies. And as far as the frequent flier is concerned: if anyone should know the rules, they are the ones, not the once-every-blue-moon-holidaymaker!