Poking into unrelated things; organizing things

This happened when I was doing my Masters. Our college had organized an event/seminar for which external scholars were invited. Now I was no where involved in the whole organizing thing and I had no clue of things on that side. I did know that there was an online registration for that event. So on the day of the event, with unnecessary enthusiasm, I volunteered at the reception counter. Interestingly, our guys had kept registration forms for the participants. I believe they were for the people who had not registered themselves online. But somehow our guys started asking all the participants to fill up the forms. Now some people patiently did fill the forms. And then I entered the scene and with utmost decency asked an elderly person, who was accompanied by his wife, to fill up the form. This pissed that man off to no limits. And the conversation between us followed:

Me: "Sir, could you please fill up this form for us?"
Him: "But I registered online"
Me: (Oh shit!) "But sir we need you to register  here once so that we can give you the ID card" (Oh yeah! like he cared!)
Him: "Why should I fill again!"
Me: silence, confused, put up an awkward face.
Him: "Don't become so inefficient from now itself! You should learn how to organize things!"
His wife: "It's OK. Don't mind. Let's go in."
Me: "Sorry sir, we'll note that"

And I learnt something that day: 

1. Never get into things which are not related to you - especially in between.
2. Always take care of the redundancy for the user - why do people need to fill again if they had registered online already?

Keep learning!