Isn't a lance corporal considered a junior NCO in the marines?Wrong.
Trump saluted the officer incorrectly - Orange Jebus isn't the Commander in Chief yet.
He then shook the officer's hand. (I watched it live.) This is acceptable.
Obama was correct in saluting the officer, then shaking his hand.
Clearly you've never been in the military.
Clearly you haven't either if you can't tell the difference between a lance corporal and an officer.