Jury nullification goes way back in this land, famously in colonial times when it was used to protect freedom of speech, later in prosecution of the Fugitive Slave Act and during Prohibition. Unfortunately, it was also abused during the Jim Crow days, exonerating obviously guilty whites of crimes against blacks. You take the bad with the good.
The power is absolute and constitutional, upheld multiple times. However, its application has been eroded by later decisions. By the late 1800s judges didn’t have to inform the jury of their power, and by the 1960s they were allowed to prevent the jury from being told in the courtroom that they had this power at all (a judge will declare a mistrial if the defense tries). This guy was simply trying to inform potential jury members of their legal power and their rights as citizens. Consider it Miranda for juries.
“It is presumed, that juries are the best judges of facts; it is, on the other hand, presumed that courts are the best judges of law. But still both objects are within your power of decision ... you have a right to take it upon yourselves to judge of both, and to determine the law as well as the fact in controversy” — John Jay, first Chief Justice of the United States
I think the tyranny is running scared.