First of all, I have to second the idea that 3.X isn't "junk." I'm still totally up for playing a 3E/3.5 game. But then again, I'd play 2E, 1E, OD&D, old World of Darkness, the FASA and Last Unicorn Games versions of Star Trek, and the West End Games Star Wars as well. Just because it isn't new doesn't mean that it can't be fun.
Second, "manipulating the rules" is not endemic to 3.X players that are crossing over to 4E. Players like that are called munchkins or rules lawyers, and they exist in every game. They've been around since before 1E and they'll be around for 5E, 6E, and so on.
Third, there's a major point that you're not addressing, but some of the other posters have: if there are different ways that that same rule could be read, it's not written clearly enough. Look at the longsword, for example--it does 1d8 damage. Now, if instead, the rules said, "a longsword does more than 1d4 damage but less than 1d12," would you think that players are trying to "manipulate the rules" by using different dice for the same weapon? Or would you think that the rules aren't written clearly enough? All the rules should be written clearly, reagrdless of being in 3.5 or 4E. And it's certainly not the player's fault that a book was poorly proof-read and edited.