Previous UN history -- particularly the historical behavior of US ambassadors and other military VIPs -- should be examined closely before judging the veracity of their assertions today.  Here is a very good example of previous US performance at that UN:
Colin Powell's presentation to the UN and the world in 2003 
h..........ttps://www.youtube.com/watch?v=ErlDSJHRVMA

Jumping to conclusions was bad in 2003 because it has led to the situations we have today in Syria, Iraq, Libya, Yemen, Somalia, etc. Because of the world's ever-closer proximity to a nuclear WW3, it is an absolutely unforgivable sin today.