Dear Avira,
That blurb from the Gaon is from the least authenticated of his writings. Your point about influence may be a valid one. But that is not this discussion. The Gaon himself studied all kinds of wisdom. There is no fear of being influenced from the truth. The only question is if the student is ready to handle it. But if he sees the wisdom in say, chemistry, what is the danger of outside influence?
I have a feeling this will be a long discussion. So keep it light. We can always yell later.