Question

[tulc]

Then explain this: Why is it that every christian states a love for God, yet many are unable to love all people?

...because we're trying to be more like Jesus but we aren't Jesus? So we fail, and that just means we have to be aware of where we've failed and work at doing better.
tulc(believes in doing our best and working to do better)

 

[RibI]

As people (not necessarily Christians), what is the single most important thing we can do to please God, based on the written word.

Nothing!