He stressed in the memo that Delta is "proud and honored" to be based in Atlanta and that the company supports the Second Amendment.
Delta's decision triggered a showdown with pro-gun lawmakers in Georgia, where the Atlanta-based airline is one of the largest employers with 33,000 employees statewide.
Ignoring warnings that the state's business-friendly image could be tarnished, Republicans in the state legislature voted Thursday to kill a tax break that would have saved Delta millions of dollars in sales tax on jet fuel.
GOP Gov. Nathan Deal tweeted Friday that he swiftly signed the measure so Georgia taxpayers could benefit as soon as they file 2017 tax returns.
As the #BoycottNRA movement spread, NRA members - including some Georgia lawmakers - wondered why Delta wasn't discontinuing any of those discounts, too.
Delta spokesman Trebor Banstetter said Friday the discounted fares had been available for a short time and were only for NRA members purchasing flights to the group's 2018 convention in Dallas.
Delta joined United Airlines and several other American companies in dropping ties to the powerful gun advocacy organisation after activists called for a boycott of the NRA's corporate partners on social media.
Deal said he plans to sign the broader tax bill, even after Senate Republicans moved to kill a tax break on jet fuel that would primarily benefit Delta.More news: Cabinet clears Fugitive Economic Offenders Bill to target big defaulters
"Our people and our customers have a wide range of views on how to increase safety in our schools and public places, and we are not taking sides", he wrote. Delta has a major hub at the Atlanta airport, one of the busiest in the world, and is a key driver of the airport's economy.
Bastian says: "Our objective in removing any implied affiliation with the NRA was to remove Delta from this debate".
State Sen. Michael Williams, a GOP candidate for governor, told "Fox & Friends" on Friday: "We had to send a message".
The Senate passed the broader tax measure 44-10 Thursday after it was stripped of the fuel tax exemption, with Democrats accounting for all of the no votes.
After the Delta decision was announced, disagreeing Georgia lawmakers, including the state's lieutenant governor, zeroed in on the fuel tax exemption element of the state's imminent tax legislation.
"While Delta's intent was to remain neutral, some elected officials in Georgia tied our decision to a pending jet fuel tax exemption, threatening to eliminate it unless we reversed course", Bastian said. "I have tremendous respect and admiration for [Georgia] Governor Nathan Deal, and thank him for the work he has done on the jet fuel exemption".
"I hope they are better at flying airplanes than timing P.R. announcements", Ralston said. GOP Lt. Gov. Casey Cagle vowed to fight back. "But will it be the dominant factor?"
Despite the day's tax talk blame game, the governor emphasized the $5 billion tax cut over five years is the day's biggest story. "I think it does not enhance our chances to get Amazon".