Maybe I'm a bit amoral, but when I introduce people I've met online to other people, parents, friends whatever, it depends entirely on how they would react as to which story they get. Generally it's either the truth, or 'we met through a friend'. Over time it ceases to be an important issue. And if they 'find out' and get a bit indignant about me lying to them, it's just a case of, "well, I wouldn't have lied if you wouldn't have freaked out!"
The guy should be understanding just explain that it's frustrating how people find these things so taboo still and that your family wouldn't be happy with you meeing someone from the internet. I'd probably say that the only people I know who don't think it's strange are people who have met up people they met on the internet themselves. So you are far from alone.
THIS SAID, how old are you? If you're at the age where you need to justify everytime you leave the house (or still feel guilty about lying about where you're going...) then please be awfully careful. Don't go far from home and meet in a busy public place, like a shopping centre. Have a friend hang around in the background who can rescue you if needs be.
xxx