From the Enemy's Eyes-Rohirrim Charge on Helm's Deep/Pellenor

[Kath]

The horse charge at Helm's Deep should have been easily defeated, or at least slowed - this scene was a bit unrealistic, but it's PJ.

Ah but these horses were travelling down a hill (correct me if I'm wrong there that's just how I saw it) at a pretty fast speed so even if the pikes did get them there was no chance that they could just stop. Also, the arrow bits in that scene looked a little unrealistic because of the suddenness with which they stop the horses.