Why George Bush, Sr resigned his lifetime NRA membership

Here's ex-president George HW Bush's public letter of resignation from the his lifetime membership to NRA, sent after Wayne "Armed guards in schools" LaPierre gave a speech blaming gun laws for the Oklahoma City bombing, implying that the victims were "jack-booted thugs" "wearing Nazi bucket helmets and black storm trooper uniforms."

Al Whicher, who served on my [ United States Secret Service ] detail when I was Vice President and President, was killed in Oklahoma City. He was no Nazi. He was a kind man, a loving parent, a man dedicated to serving his country -- and serve it well he did...
...I am a gun owner and an avid hunter. Over the years I have agreed with most of N.R.A.'s objectives, particularly your educational and training efforts, and your fundamental stance in favor of owning guns.
However, your broadside against Federal agents deeply offends my own sense of decency and honor; and it offends my concept of service to country. It indirectly slanders a wide array of government law enforcement officials, who are out there, day and night, laying their lives on the line for all of us.

Letter of Resignation Sent By Bush to Rifle Association