I wouldn't ban the OO march outright, but under no circumstances ever should they be allowed to march past a Chapel or an area where they would be unwelcome. We would be going down a dangerous road if we started banning people's right to celebrate their faith (or even their weird kulchurr)
Let nature take its course, the OO is a dwindling organisation, toiling for cash, with its numbers getting fewer, if some of their bands attract trouble then they should be banned from marching, if there is no trouble or intimidation, they can march away.
Imo, banning them may even breathe new bitterness amongst them.