I disagree. Having discovered that, no matter how strong the online connection, there is no way to know, in advance, if there will be chemistry in person. In my own experience, there was real chemistry 6 out of 18 times, or 1 in 3. When it's not there, both people usually realize it.
Still, if you planned a nice first date, there's no reason to be rude or abrupt. There's always a value in getting to know a little something about someone else, and completing the evening as planned, leaves both people feeling "ok" with the experience, rather than "yucky" and "rejected". It's merely common courtesy to go ahead and have dinner, or enjoy the music at the blues club, or the game that you have tickets to go to. To do otherwise, it seems to me, is somewhat crass and ill mannered.
Yes its a bit ill mannered to just end the date. But if the woman has decided that she doesn't want the guy, the guy is just going to be further encouraged by a good date. I found the idea that the woman decides within 2 minutes on superficial or subconcious factors to be a bit depressing. It's the quality of the relationship that makes me want to kiss someone, not what they look like within 2 minutes.
Just because one person feels chemistry, doesn't mean the other person is feeling the same, but it is easily assumed!