can I tell the cops I am happy with those people being on my land?
You're assuming that a police officer will accept your formulation of the question as being about whether you are "happy" or not about the presence of the protesters.
The most likely structure of the interaction is that your easement-holder will ring the police to say that a trespass is occuring which interferes with his rightful use of the land (via the easement).
The protesters may be asked whose permission they have to be present. They will either indicate that they have none, or they may say they have permission from you.
The question will then be put to you: are these visitors present with your permission, or are they indeed trespassers? Or, if they came onto the land without explicit permission, do you ratify their occupation of the land by granting them permission now, or are they present without your permission now?
If you grant permission, then you may become liable to your neighbour for frustrating the use of the easement. And if you do not grant permission, then the police may well remove the protest.
