More stupid people problems

I would have to say the toughest thing about my job is dealing with the stupid people. I realize this makes me unique from everybody else who has a job by about 0%, with the only exceptions being certain sects of monks who are bound by a vow of silence but those guys don't show up in the census.
One of my favorite things about life is how we all know the stupid people are out there but none of us are them. We can point them out in a crowd, we can mention them by name (many of them are our friends and relatives) but none of us are actually stupid. The stupidest person in the world can be in the middle of doing the stupidest thing they've ever done and they'll be looking at someone else, shaking their head sadly and thinking to themselves "look at that idiot over there".
These are the people who make my job less than a pure joy. Specifically, the argumentative stupid.
I work in customer service, which is not as bad as it might sound initially. I like helping people solve problems. Better yet, my employer affords me the resources to do so. It's not a bad job at all. I sincerely enjoy it. But every now and then, I get someone who calls for help and then wants to argue with me. This is something I simply can not comprehend. Let me give you an example:

CALLER: Hey, when is the thing?
ME: It starts at 8:00PM.
CALLER: Are you sure? Because I read something on the internet that says it starts at 7.
ME: Yes sir, I'm sure. That event definitely starts at 8.
CALLER: Well, then why did it say 7 at whatever.com?

All right.

1. You called me with a question. If you felt like you already had the info, why did you call?
2. I don't work for whatever.com. How should I know what they publicize or why?
3. I'm here, at the place where the thing is taking place. I think I have a better handle on the situation than whatever.com. I presume that was a factor in why you called me.
4. If you don't think I'm a credible source of information, why did you call me?

Sometimes these people will argue with me about directions, as in how to get from where they are to where I am and all I want to say is, "Well, I'm here, proving I know how to get here, and you don't, so...". Of course, I can't say anything like that or any of the stuff up above. I don't want to get fired and I don't want to upset anyone and mostly I don't want to get fired. This puts me in the position of having to argue without arguing, also not to be condescending. I have to because it's my job to impart the correct information and if I don't argue, I won't be doing that. I'll be failing to provide the service which I'm paid to provide. It's difficult and happens enough to cause frustration, which if unchecked, can come out in dealing with people who aren't stupid and argumentative and don't deserve to be treated as such.

So what do I do about these stupid people? Eh. Nothing. I just complain about them on this blog every now and then. It's cheaper and more effective than therapy and unemployment.