I am afraid I do have an issue with people coming on private land uninvited. I would not dream of going in someones orchard, walking round and helping myself to their apples, so why should they come on my field and pick my blackberries etc??
Since the right to roam came in, we have had quite a few people think that includes our fields (it does not!). If I catch them, I tell them politely they are on private land, direct them to the footpath and most apologise at this stage, and leave. Some start to argue they can walk where they want ......one more polite asking them to leave, and then I tell em proper!!!!