"Scientists should indeed recognise that their theories are provisional, rather than "true" in an absolute sense."

Good scientists do. But even good scientists are human beings, which is their finest attribute.

"But if course that doesn't stop them holding on to them even when evidence seems to disprove them, and from trying to find ways to cast doubt on that evidence."

Which is why science insists on peer review of evidence. As I say, you have a fair bit to learn about what good science gets up to.