I'm sorta guilty of this. I GM a lot so I'm very familiar with monster stats and I sometimes get a bit enthusiastic when I know what a monster is. I'm not that bad but sometimes when I start jumping up and down and clamping my mouth shut the GM gives me the hairy eyeball. As combat progresses I generally don't use OOG knowledge unless we're getting our butts handed too us. Mostly I'm pretty good though. Mostly.
For dealing with meta-gamers I find that on the fly substitutions can work if you pay attention to what you are doing. Change energy types and vulnerabilities, switch up what breaches DR. Minor alterations that don't change the power level of the creature are totally acceptable in my book.
Just as a guideline I generally go with Knowledge (appropriate) DC 5 + CR to reveal basic facts (type, HD range, attack bonus range) and add some more facts per 5 over the DC. As an aside I do the same thing for polymorph, DC 10 + creatures HD.
I'm not a fan of trying to control players with sit-down talks and heavy-handed rules about what can and cannot be spoken at the table. The moment you do that, the game stops being a game and starts being about the amount of power one person has over another. I much prefer the approach many have suggested here. Namely, deliver the unexpected. Use the outbursts to your advantage. If the player claims that the monster can only be hit by silver weapons, immediately give it some DR and switch that up. Never name the monsters. If someone says that a monster isn't following the rules, apologize for their misinterpretation. Also, don't forget that there are lots of monster books out there. Tome of Horrors, etc. Throw the freaky stuff at 'em.
Be careful describing the sit-down talks as "trying to control players." You're either intentionally misleading people reading this thread or you don't understand it. No one's suggesting controlling the player; instead, we're recommending sitting down and discussing the problem like adults with everyone in the group involved (not DM vs player). And make no mistake, it's a big problem.I'm not a fan of trying to control players with sit-down talks and heavy-handed rules about what can and cannot be spoken at the table. The moment you do that, the game stops being a game and starts being about the amount of power one person has over another. I much prefer the approach many have suggested here. Namely, deliver the unexpected.