Errors are forgivable - but prefacing those errors with statements like “indisputable”, “without question”, "these are God's dates not ours”. “this is not of man but of God”, “anyone who disagrees is against Jehovah”, and then disfellowshipping those who don’t swallow it all, is another matter. Sure scientists make mistakes, but they do not do that.
Follow this up with lies, deceit and misrepresentations to try and cover up those mistakes compounds the sin and shows anyone with an unbiased reasoning ability that the Watchtower a manmade organisation, not God’s.