What? Whoever wrote that article has some really strange ideas!
I do think that those really long (and normally square) acrylic nails look really trashy, and those are often french manicured. But normal looking nails with a french mani can look great! It's all to do with the overall look of the nail, not the polish! Like, for instance, if I'm going to wear a bright red on my nails I might file them down a bit so they don't look skanky, which they might if I left them longer.
It's stupid to say an entire style of manicure is slutty! It completely depends on who's wearing it, and how they're wearing it!
And anyway, do we really believe that guys pay that much attention to our nails???