There's a difference between learning a skill and learning a skill while remaining human. You need to decide which you want.

Do you have preconceptions about what thinking should feel like? Do you want your instantiation of the skill to be more similar to other parts of your mind, or more similar to other instantiations of the skill? To get really good at something, it helps to remove constraints about how you achieve it.

Science before the mid-20th century was too small to look like a target.

Basically what JoshuaZ said, although science can also be a victim of convenience rather than just ideology. Using science for status gain without adhering to its rules also counts as targeting it, e.g. plagiarism.

I don't really mean that science never looked like a target before the mid-20th, but it's definitely much more of a target now.

Science before the mid-20th century was too small to look like a target.

In this case I interpreted it to mean that there are many people now who specifically target science as bad (i.e. complain about "scientism" etc.) because science is a large, successful enterprise. He is asserting that before the mid 20th century science was not prominent or successful enough to bother being a target of attack. I'm not sure he's correct here, but the basic notion is plausible.

There's a difference between learning a skill and learning a skill while remaining human. You need to decide which you want.

Learning how to transplant a kidney is much easier when you have a few dozen people to experiment on. (I think that was the idea, anyways...)