Mass Zombie Pigmen Aggro Lags the Whole Realm

*What I expected to happen was being able to use the Zombie Pigmen farm while the rest of the realm can do what they want
*What actually happened was the lag was so unbearable that we've banned using zombie pigmen for xp.

Steps to Reproduce:
1. Spawn Multiple Zombie Pigmen on a Realm
2. Hit one
3. Try making a redstone clock, tick lag.