Like some have said, if you can't handle that, you need to go over to news, where you'll never run into a pissed off politician.
Seriously speaking here, Tom Petty has a great response, but it's only effective in your case, I believe -- since you are leaving this paper. You have no worries about future access.
I apologize to pissed prep coaches. In one instance, a coach had problems with a story done in the pre-season, and he never mentioned it to me until like a year later. I told him I wished he had brought it to my attention first, so that way I could have run a correction, if one were warranted, or could have written a follow up story.
I also invited this one coach to write a letter to the editor, yet he didn't want to do that.
I treat these coaches well, because their jobs suck, too. If they see you as fair and "on their side" as much as possible, they'll call you in the middle of the night and let you know how they were forced out when the time comes. And that's a good story to have written.
Also, coaches have gotten pissed at me for writing stuff in briefs about their team. Generally these are the coaches never return my calls, refuse to provide me with adequate information on a timely and consistent basis. This is where I become rather assertive.
I calmly tell them that they have my phone numbers, yet I have not heard from them until this point. I explain to them that I have left them messages, and if I could get as much as a 10 minute phone call each week, then they could "control" what gets in the paper about their team.
I usually explain how I have 15 or so schools to cover, which is darned near impossible, and their 10 minute or so phone calls each week comprise much of the information about every team in the paper. And tell them I am not perfect, and rely on their cooperation in order to get the job done. When they don't cooperate, I don't see that they have any reason to bench.
One coach was so forking stupid, he had no idea that a letter to the editor is something that is printed. We printed his letter, blasting me out, blaming me for black death.
My editor put a note on the end of it that explained that this coach was the most uncooperative coach in the paper's coverage area. That we had a record of 100 or more phone calls that were not returned in just a few months time, and the only reason we still included his team in the coverage area was because of the countless emails we got from parents requesting coverage -- and this football team wasn't bad. It really made the coach look like an idiot, and despite consecutive 11-2 records, and more than 100 wins in like 12 years, this guy was fired.
It involved other things, mainly he was a poor representative of the school district, or so the school board said when they surprised everyone by announcing in a press release that his contract had not been renewed. So he pissed others off, in addition to myself while trying to cover his team for two seasons.
But, explain when you need to, that you're human, you make mistakes, and you need their help to get the "right" information about their team in the paper. It helps them to help you, or that's my opinion. Also let them know that they can call you and complain, without fear of retaliation. It aids access for future juicy tidbits. Treat them with respect and fairness, and you'll get the same in return.
This method has worked very well for me, sometimes to the point where I became very good friends with some coaches, football, baseball and basketball. In one small town, a weekly I worked at, I was regularly invited to Sunday afternoon barbeques at one coaches house. After a while, I finally accepted and when I got there, lo and behold, several coaches from other schools (along with their families) were there as well. It was kind of fun to drink beer and hang out with them, and I got lots of good information from them -- nothing that was on the record -- but stuff that let me forsee things that were coming down the pipeline, i.e. star player for Podunk won't be there next season because he's addicted to oxycontin, long time coach is retiring b/c he's got cancer, several kids were arrested for pulling pranks, kicked off winning football team that slid in the polls after the kids were booted, and a whole host of tidbits on some of the unethical practices going on in this state's school system.
This kind of knowledge provided me with future questions to certain people that was on the record. It allowed me to know who to ask and what to ask. So dealing with pissed off coaches is tricky business. When you do it poorly, as some have done that I know of, you get nothing in the future and run the risk of the competition beating you on everything.