The devs already banned nichehash users a few months back because the difficulty alogrithm was keeping the difficulty stuck at a high levels for several days even though the big hash miners or nicehash users already left. That problem was addressed by using the Sumokoin improved algorithm which adjusted the difficulty algorithm quickly depending on the network hash rate. A fork of Intense was made and after that, the nicehash users were allowed again.

During the time that Nicehash was down, we saw big spikes of mining hash rate going into the network and the main pool. Even without nicehash users, it was clear that there were big miners coming in when difficulty was low and going out when it was high. I think banning nicehash users now will only benefit those with big mining farms. Nicehash at least allows us ordinary users to get a big hash rate even for a while without spending a large amount of money to build mining rig farms.