Apom, my job requires background checks; my previous job, as a Navy officer, required background checks. I have held security clearances suffiicient to gain access to the CIA building, had work required it.
I have had years of military firearms quals; concealed carry licenses in three states; I have attended training courses run by top tier instructors.
The government has entrusted me with thousands of lives and billions in equipment (former Ship's Weapons Coordinator, Force Over The Horizon Track Coordinator, and Tactical Action Officer aboard a NIMITZ class carrier).
I hold a current Airline Transport Pilot certificate.
I do not fear background checks (or training requirements) because I worry about passing them - I am kind of a poster boy for people who should easily meet background and training requirements in any jurisdiction in the US.
I fear background checks and training requirements because they allow a tightening of the noose on the Second Amendment; I fear background checks and training requirements because they allow a way for the political equivalent of the country club set to keep "those people" from becoming members of the right to bear arms club; I fear background checks and training requirements because they turn a right into a privilege.
Instead of positing that the only people who fear background checks are those with criminal histories, I would posit that the only people who do not fear background checks are the ones who have not thought it through.