I don't know how you could have read the part about how to discourage meta-gaming, because meta-gaming is bad, and come away thinking that it isn't against meta-gaming.
3) Inspiration is a metagaming mechanic.
The degree to which this is true is going to vary from table to table. You
could use it to model
inspiration, which is a thing that exists within the game world and which the characters are aware of, and which is reflected in the ways inspiration is gained and spent. Or the DM could ignore the mechanic entirely, which is another option in the book. Or I guess you could treat it as a meta-game player resource, if you really wanted to.
If you have convictions about how other people choose to enjoy harmless games, yeah, it makes you wrong. Nobody needs your permission to play games the way they want to.
It sounds like there was a miscommunication somewhere. I'm not against
other people meta-gaming, at their own tables, as far away from me as possible. If you can have fun playing FATE or Savage Worlds or this new Conan game, then that's great. I just don't want it anywhere near
my table, because it directly conflicts with the core principle of role-playing, which is that you make decisions
as your character and out-of-game factors are
irrelevant.
When I say
meta-gaming is bad, I mean it in the same way that
pineapple on pizza is bad.
I find it supremely distasteful, and I can't just ignore it because it ruins the taste of everything around it, but it's not a moral judgment against people who like it or anything.