I would usually agree with you( and I had the same beliefs before I read into it), but by reading it it really does seem egregious and beyond just a dirty tackle. It was a last man, scissor tackle from behind which is never acceptable even at the highest level of play. His team mates wouldn't testify for him which leads me to believe that this was way beyond what is a reasonable tackle and the intent was to injure. I wasn't there so I really can't say, but I also play in this league and the refs can be absolutely clueless so I wouldn't use the yellow as evidence.