Sounds like another public school teacher with an agenda. I would suggest giving your grandson some outside resources such as a short course on the US Constitution, and a general idea of what a real debate is supposed to accomplish.
My son went to public high school after 8 years of home school and we finally had to tell him that what was most important at that school was to regurgitate back to the social studies and English teachers what they WANTED TO HEAR, if he wanted a good grade. The actual education of my son in these two areas, unfortunately, continued to be provided at home, not in the school.
rant over ....
sigh .... that said .... all of the above helps and resources sound like good places to start!