Why Was There Not a Penalty Called for Hitting Ben Below the Knees?

On the interception play that Ben was pressured by a D lineman, who was on the ground, reached out and almost tripped Ben. I thought any contact below the knees was prohibited unless he was acting like a running back. Moving sideways in the pocket should not be considered that the QB is a runner.
The caliber of officiating is deteriorating instead of getting better.
Cam Newton absolutely got drilled by Denver with no penalties.
Is it that there are more camera angles now so the errors are more noticeable?