Its hardly desperate and its probably the most obvious answer to the question.
What is the difference between what Lewis did vs Mark and what Vettel did vs Alonso?
Mark was squeezed onto road.
Alonso was squeezed into crash enducing, potentially race ending dirt and grass.
One driver created a dangerous situation for another driver. The other didn't.
One was part of an exciting/committed overtaking move, the other was aggressively shutting the door on what could have been an exciting/committed overtaking move with more dangerous consequences.
The stewards take racing discretion as well as a rule book into their booths come race day and they use them both to make their judgements.
If your actions create a more dangerous situation than anothers, then yes, it is more likely that you will get the penalty over the person who didn't. If Lewis squeezed Mark into grass/gravel and he crashed/beached the car, you can bet there would be a penalty of some sort.