There are two kinds of people perceived as “bossy.” The first really means well. He wants to see something done right, and he’s objective in his approach. He looks at facts and determines what makes most sense. He actually is smart, is usually right, and wants to help. If you politely decline his help, he’ll be a bit puzzled, but he will back down.
The other kind of person perceived as bossy is controlling. Some controlling people are competent and are usually right; and others aren’t so bright. But either way, the motive is the same: To be in control of others. The agenda is usually one of gaining the credit or the spotlight rather than simply liking to see things done right. If you politely ask a controlling person to back down, he won’t take it well.
It’s unfortunate that the second kind of bossy person gives the first a bad name.