Grabbing a Sword's Blade is Indeed Stupid

 If you have a nice gauntlet you can push away an enemy's stopped blade, yes, or do half-swording.

 However, this is dumb. Don't do that. (Cue midwit meme: it looks stupid because it is.)
 If I try a mordhau on you, you block my forward hand, then grab my hilt, then yank: now you have two swords, and I probably have cut-up hands instead of a weapon. What, I'm going to contest your grip on the hilt by putting tremendous pressure on the blade? Even if I somehow do, you can try to scrape my hands off with your own sword. 
 Yes, using leather you can safely swing a sword like that...as long as nobody is trying to stop you. Murder-stroke is a good name because you get murdered if you try it.
 If grabbing the blade with two hands could contest a hilt grip, you would do that in the first place. Keep your sword sheathed and take mine when I tried to pull it.

 You know, fantasy works always say maces and warhammers take tremendous strength. This is indeed true: someone is going to grab these blunt weapons and try to yank them out of your hand. You need to be stronger he is so he can't.

 One-handed warhammers in particular are idiotic. The head provides a lovely point of leverage which the handle doesn't; unless you are Hercules, you better win on the first swing because you're not going to get a second. Axes don't normally work this way because there's a risk of the wielder yanking it back at the wrong moment and at the wrong angle; indeed instead the axes are often used as hooks to disarm the other guy. Again you need to be the fighter with more STR. Even if the opponent gets a firm grip there's ways and means of lunging the blade into their elbow or whatever is handy; body slam them, the blade is already pointed in the right direction. One-handed warhammers are perhaps mounted combat only. Two-handed warhammers, of the kind used by folks in full plate, are just fine. Anyone trying a disarm is going to use one hand, and your two hands will overpower that every time, so he won't go for the disarm in the first place. Most likely maces have sharp flanges not because it makes them deadlier but because it discourages the disarm. 

 Speaking of maces, if someone comes at you with a club and you have a shield, block, bind, wrench: now they don't have a club. Throw it away and take out your own disarm-discouraging weapon. Hence, ogres and giants: yeah you can't block an ogre's club, and if you try to grab a giant's club, they'll just pick you up along with the weapon. Instead of you disarming him, he'll be unlegging you.

 Halberds are both two-handed and move very quickly due to being long, meaning you can't really afford to block them. They can down someone wearing plate in a single blow, so, yeah, have fun with that.

 Spears are hard to bind and if the disarmer's grip slips, his hand will get sliced by the head. You can push it away by the shaft and stuff but it doesn't help much, the wielder has to retract it anyway unless he intends to tickle you with the blade.

 However, if e.g. a woman is using a spear, your grip won't slip. You can just take it. Almost none of them will be stupid enough to try to attack you with it in the first place. Their genes know it won't work.