How boldly had Les taught eternal security when the man called?
At that time, he had not yet come out as boldly as he later did. He was only alluding to an eternal security for the true believer, not fully declaring it outright, when a gentleman from Oklahoma called and questioned how he could do that.
Les explains that he had been on the Tulsa station only about a month or two when a gentleman from Oklahoma called. The man was not angry, but he was a little upset because Les was more or less alluding to eternal security for the true believer. Les acknowledges that he had not yet come out as boldly as he has since, and the caller asked, "How can you do that?" This arose in the context of I Corinthians 1:6-8, where the testimony of Christ was confirmed, and believers are confirmed unto the end and stand blameless by grace.