Rhetorically, what’s wrong with feeling good about being Christian?
There is nothing wrong with feeling good about being a Christian, but that’s not the Gospel.
Yes, it’s great that God has saved mankind, through the blood of Jesus Christ and, all I have to do to be saved is to confess my sins and accept Christ. But there is also the matter of, when you do wrong, you are supposed to make amends to the person you have wronged. I have never heard these people talk about that, never.
The problem is that with Meyers, et. al. they offer Christianity as a means or way to feel good, to be successful in life. One does not come to Christ for what they can get; except for forgiveness of sin.
The Christian is promised peace-peace with God. All that will live godly will suffer persecution. The key is, for what is the Gospel being offered? Is one aware of their sin before God, and that knowledge is a cause of alarm, for they see it is an offense to God, which will result in such a terrible judgment that they also know they cannot bear to endure it. They also are aware of the neglect of their duty to worship God, and they understand this to be a serious matter.
Unbelievers, on the other hnad, do not conider their neglect of true worship as anything important as a violation of a command of God; none of which they take seriously anyway.
Meyers (and others of her stripe) offers Christianity as a means to get goodies from God, not as the only way a sinner in desparate need of a savior can obtain frogiveness and removal of their sin. The Gospel is God's means of removing a person from a state of being God's enemy to becoming one of God's redeemed children. The Gospel is the only way to restore the right relationship with God that sin destroyed. It is not simply a way for you to feel better about yourself.