For sure Fox et al. have been pushing the idea that scientists have biases, but it can also be true that science has become more biased.
Update: a little evidence. This doesn't cover change over time, but it strikes me as fairly extreme, unless you are willing to go very far down the "reality has a liberal bias" road: https://github.com/hughjonesd/academic-bias
Update: a little evidence. This doesn't cover change over time, but it strikes me as fairly extreme, unless you are willing to go very far down the "reality has a liberal bias" road: https://github.com/hughjonesd/academic-bias