> demonstrates that your judgement about what is a bad motive for entering a scientific field itself involves a value judgement.
Yes, I judge people who try to corrupt our view of science. I never denied that.
> our concern for bad motives is separate from the question of whether science if value-laden (which it is)
Science having value is exactly why I don't want people to corrupt it. If you agree with me that science has value then you should agree that we should try to stop people from corrupting it.
If you argue that we can't judge who is corrupting, then I'd argue that you are so out there on the clouds with your definitions that we could just as well argue that a random youtube commenter is also doing science and that is a good thing and that we can't really say that youtube commenters are worse scientists than the people at universities since that is just a value judgement.