I watched the video, expecting to see some serious damage from some of the comments above. The video shows a guy clearing bracken where it has completely dominated a hillside below a woodland, which is generally considered to be a land management issue.
Obviously I watched it with the sound off in case he said something youthful which would anger me, but genuinely his trail was clearing dead bracken with occasional bramble in the winter. There was a small area of heathland habitat at the top which appeared largely unscathed. The loam scraping under the bracken is arguably beneficial in terms of exposure of bracken rhizomes and reducing regrowth to allow other species to colonise. It’s winter, so the disturbance isn’t a ground nesting bird issue and the trail went across the hill (ish) so erosion probably won’t kick off.
Perhaps it was more by accident than design, but the location and timing of this little activity seems ecologically neutral and could have been much more damaging elsewhere, permission debate aside. Just for balance, like.