This is a very natural & logical thinking. But unfortunately, a few decades of research has also shown that this is also
the wrong thing to do, because by knocking people down (i.e., those you
perceive to be blocking you), you are turning the evacuation process into a "competitive evacuation" -- a "free for all" where everyone is pushing those in front, stampeding in a rush to get to the exit door.
It might not be a "guy getting a bag" in front of you, but maybe a mother trying to attend to her baby, or a kid that has stumbled, or an elderly person who's confused. Or maybe even a flight attendant who's assisting someone else. Are you going to knock them all down?
The research findings are a bit counterintuitive. But basically, if you have a small opening (door), and a large number of people whore are
competing to get out of the same door, you will end up in a "jam" situation where everyone blocks everyone else.
So instead of getting out faster, you and everyone else end up getting trapped in the cabin. This has in the past resulted in total blockage of the exit doors, leading to numerous fatalities.
For further reading see the Cranfield experimental research done in the UK some years ago in response to the
1985 British Airtours Flight 28M tragedy in Manchester. This was a rejected takeoff situation after an engine fire, where most passengers on the flight perished right on the runway due to smoke inhalation, as they were unable to quickly exit the plane.
There should have been enough time to evacuate the plane even with some door problems that they had, but the free-for-all "stampede" to the exit door trapped numerous people inside.
Cabin crews are trained to be extremely assertive in preventing this from happening and to maintain an orderly evacuation.
Your best bet to exit, as well as the best bet for all your fellow passengers, is to follow cabin crew instructions and to have the most orderly,
cooperative exit possible.