"...Our security emanates from the justness of our cause..."
"...the righteousness of our cause must always underlie our strength...."
The answer is that they are complete opposites. The first is completely untrue. The second is completely true. Our security does not come because our cause is just. There are many just causes around the world that offer no security from a dictators gunman or a Nazi oven.
However, our strength must stand on a foundation of a just (or righteous) cause. To have strength, but use it for evil, is evil. To have strength and wield it irrationally, is sinister. We must ensure that the cause we fight for is just, otherwise our strength is just brutality. How odd that these very similar statements, both spoken by Presidents of the US, could be so contradictory.
The first is from Obama's Inaugural Address. The Second from JFK's undelivered speech in Dallas the day he was assassinated.