is having fire alarms placed in your home a state law or federal law?
If you parked in front of a fire hydrant you deserve to be ticketed. Take responsibility for your actions. You can fight any ticket you want, that doesn't mean you will win. When everyone knows you don't block fire hydrants and then you go and park in front of one anyway? You get what you get. He didn't give you a ticket for bumping into him, he gave you a ticket because you were illegally parked.
Easy. Go back to where you got the ticket and photograph the exact spot, if what you are saying is sufficiently true. Then go to your court date ready to present it when your docket is called. *IMPORTANT* If you have enough time to, go to the courthouse and have them reschedule your court date. Tell them you are going to be out of town that week and simply CANNOT appear. This almost ALWAYS throws off the officer who issued you the ticket (remember the ticket contains only the original date). Over half of the time, police don't show up to reset court dates. Guaranteed. So if he doesn't show up, it gets thrown out. If he does show up, present your photograph and state your case. Maintain that you are sorry you broke the law, but explain your extenuating circumstances. Heads, you win tails, you win.