I have heard that argument against stream access all my life and, although I'm sure it happens occasionally, "all the time" is an exaggeration IMO.
For over forty-five years I have owned and reside on property with substantial river bank along the blue ribbon west Gallatin River, near fishing access parking and with a bridge marking the corner of our property. My fence is back from the river so there is a path to walk the bank and it is frequently used. Having met and visited with fishermen from all over the world and in significant numbers in the summer, I have had negligible problems with litter, property damage, or disrespect during that span of many years. I am convinced that fishermen are there to fish, recreate and enjoy the river, not to create problems. I am not only a strong advocate in support of Montana's great stream access law, I am also a landowner who appreciates access and the attitudes of the fishermen who enjoy the river.