Because there are many learned people who are Christians, and among them are some scientists. This isn't a Christian claim. This is a scientist's claim.
Do you consider doctors to be scientists of a sort? I can't tell you how many doctors believe in God, and pray each day, often with families. That's not a claim either. It comes from the doctors who are believers.
Would you let us know, please, who "they" are? Who are these people who are making false accusations about scientists? You refer to this "they" group, like we should already know who you are talking about. Give us more. We need to learn!