I was just wandering whether anyone else noticed how the horsemen, when they charge, never get hurt when they are facing spears. It's probably something to do with their instinct but when Haldir's men charged lots of them got speared but in Eomer's charge and the Muster of Rohan they all get off unhurt?
If you are referring to the end of the battle of Helm's Deep : the fact that Mozes/Gandalf the White was with the horsemen and blinded the Uruk-Hai with his light, helped a lot in reducing the casualties.
Also that is why in the film when the army of 6000 Rohirrim charged against the Orcs of Pellenor who only have short jagged pikes, capable of doing limited damage compared to the Pikes of the Uruk-Hia, that is why they were simply swept away but the Horsemen. I think alot of people forget the shear forces a 40 stone horsemen charging at you at perhaps 15mph or more, clad in armour would do.
Also don't forget that the Rohirrim often had bows whilst riding so it would be probable that perhaps 40 meters or so from the pikemen as they are charging they would fire arrows at the front rows of pikemen to thin them out whilst there charging.
I thought a great deal about those pikes as you call them and wondered how on earth any horse could go past them without being skewered.
Don't worry. Gandalf the White changed them ghastly pikes all into lollipop sticks with marzipan points right before impact.
Never ever would Whitey risk his Shadowfax to be hurt now, would he?