The Hammonds were convicted of lighting brush fires to cover up the evidence of illegal poaching. 
 

"Witnesses at trial, including a relative of the Hammonds, testified the arson occurred shortly after Steven Hammond and his hunting party illegally slaughtered several deer on BLM property. Jurors were told that Steven Hammond handed out “Strike Anywhere” matches with instructions that they be lit and dropped on the ground because they were going to “light up the whole country on fire." "

The sentence they received was the minimum allowed sentence under the law.  The law, in turn, was the direct result of politicians "getting tough on crime". So, no discrimination, just the Rule of Law.

https://www.justice.gov/usao-or/pr/eastern-oregon-ranchers-convicted-arson-resentenced-five-years-prison

Stephen J. Remington