Some observations on this thread. I came to boating rather late in my life, starting with a power boat about 10 years ago. I have purchased 5 power boats, each one a little larger, finally ending up with a 30' twin engine cruiser. Loved to cruise the Pacific Northwest, San Juan Islands and in to Canada. The Admiral and I moved to Colorado just under 2 years ago; sold the cruiser and purchased my first sail boat (Catalina 22 MK II), which I have been "sailing" on Lake Dillon, CO. Bottom line ... sail boats are MUCH more difficult to learn how to to use. Significant learning curve, on which I feel I am still at the bottom.
So, I think that the power boaters that have taken center stage on this thread tend to be the arrogant newbies who would not consider a sail boat due to the difficulties involved. I was able to purchase each of my power boats with VERY low hours on the engine(s), most likely because these folks couldn't even master the power boat. I can tell you that no self respecting power boater would ever use the dock as a stop. Just plain bad form. I would be very embarrassed if I did not make a "clean" dock approach, forwards or backwards. It is a matter of pride.
As for helping with dock lines, I belonged to a club in Seattle and it was expected that you would always walk out and offer to help a fellow boater (power or sail) as they approached the dock, and I always did. Some needed it, many certainly did not.
Overall, I unfortunately agree that the fraction of power boaters that are untrained and perhaps even arrogant may be greater than you might find in the sail boat community. Based on my experience, it is likely the result of the humbling learning curve involved in sailing; many rookies likely quit early on. You can get a great ride in a power boat without knowing what you are doing ... which often reveals itself during docking. That said, my interactions with "seasoned" power boaters has always been respectful and informative.
My two cents ...