You take away blocking on the Pike/Long spear and it will be the end of those weapons being used as infantry support for the vast majority of the people using them. They would then be completely a anti-cav weapon at that point.
It would actually make the weapon ONLY used for infantry support and cavalry and not able to get kills 1v1 as easily as it does.
The speed/damage/length ratio of those weapons are off the charts, hence why you see all the prostar players running around with them now. I would also like to see the long awlpike included in this.
Pikes are supposed to suck 1v1, its hard enough with a short weapon to even get near them in a group let alone get a chance to attack without being turned into swiss cheese. At least if they can't block then people rushing pikes will get 1 swing in before they die. If they remove the ability to block keep the stats the same and keep it a 2 slot weapon to allow for backup weapons, also keep it non-sheathable.
I think you'd have to be a pretty big idiot to not be able to block a sideswing with a 5-8 foot piece of wood. Overheads would also be pretty easy, but I can see thrusts being an issue. No polestun and 3 slots would be more than enough nerfing, why remove block too?
If you want to use realism argument then:
Pikes weigh a lot and are really long and clumsy weapons. Normally they are stabbed into the ground with the user only holding it up for charging enemies to get impaled on. Blocking with one is nearly non-existant. The M&B version of a pike spin 360 face stab at 2 foot range doesn't exist, infact if you can get a pike type weapon that meets the specs, and can successfully jump 360 and stab something 2 feet away from you with it I will allow you the luxury of punching me square in the nose.