What John said was a stupid thing to say, this was the 60's and a very different time than today. People actually believed in God and practiced religion much more than today. What John said upset a lot of people and to simply put what he said 40 plus years ago off as something minor that upset a few people is not proper either. John's explanation was what he meant to say was in his mind, people thought The Beatles were more popular than Jesus. It came across quite wrong. John of course was wrong but from his perspective, the crazy fans and adulation they had every where they went, it's easy to see his point. Fact is then, and now, there are many more Jesus and God fans than Beatle fans.
The quote said, it was a "boast by a young man grappling with sudden fame". I think sums it up very well. Remember this is the same year the Vatican also said that we should accept aliens from other planets as our friends.