Great post. I wholeheartedly agree. I do fertilizer applications for a smaller guy in town. Any time that he gets something that is out of his comfort zone, too big, or too far for him, he gives us the lead (about to start a 10k drainage job on one of his accounts). One note though, be honest and loyal to them. A couple of his customers have called me and asked me to take over. Good accounts. You have to say no in that situation even if they are your target market. It will pay off in the long run.
Another side of the situation is that we are a growing company. About 15 employees currently with jobs posted (yes, going into winter). I have a skid, mini skid, and tractor, but don't have an excavator. If I need one, I call another landscaper who has become a friend of mine. He doesn't have a skid, so guess what? If he needs one, he just calls me. We have a great working relationship. I am behind right now so he is going to do an irrigation install for me on a commercial site, and I am going to hydroseed 9 acres for him in November.
You are right, everyone is not the enemy. Respect those who respect you. they can be an asset or a referral in the future.