Peacock won't run himself to death.
Bad news, that is just how guineas are, they can get pretty mean and cause problems like this. It is also very possible the guinea will turn the tables on the peacock and end up making life very miserable for peacocks, guineas will do great harm if they are harassing birds and are able to corner or completely wear one out to the point it can't move much anymore. You do need to worry when guineas start to gang up on other birds.
I also had free range chickens, peafowl, turkey and guineas. There were "no problems at all" for the first year after the guinea pair first came here. Then the male started harassing all roosters.. he damaged ALL rooster tails. For a couple months, it was just roosters.. but when they had babies and they were full grown, they started harassing all chickens and the father started going after the turkeys(believe it or not.. the turkeys became very frightened of them.. they were relentless!). But they left peacocks alone for some reason.. until for unknown reason they seriously tried to corner one male and very much looked like they had the intent to actually kill him- they were 'body slamming' him every time he tried to stop to take a breather.. and the males would just about get on top of him and bite his face/head. That was the last straw.. clipped wings on the guinea males.. which helped a lot- birds were able to escape them easier.
My last straw was when one of the confined peafowl accidentally got out... they went CRAZY on it and caused it to fly away before I could get it back inside.. they were on it like burning glue. Sold off all guineas except for a pair and one white daughter and kept them confined to a pen by themselves, permanently. Enough was enough. This is almost a year, still think of getting rid of those three too.. the male still acts very aggressive to birds in the next door pen or anything walking by.
