If the concept of the universe being deterministic interferes with one's concept of free will, then one of these must be true:

• the universe is nondeterministic, or has nondeterministic elements
• one's concept of determinism is incorrect
• one's concept of the impact of determinism on one's own free will is incorrect

But of course, that begs:

• ones concept of free will is incorrect

But that cannot be, because your notion of free will is for you to decide, even if the universe is somehow determinate.

But that doesn't mean the universe is or is not deterministic, it just means one or more of the above three things.

Ultimately, though, I was not making an argument concerning the fundamental nature of free will and determinism, or whether or not the universe is deterministic. I was arguing for completely processing fundamental concepts before you accept them to be true, because often times we accept a lot of false implications alongside the true things we accept.

One's world view holds immense power in one's own life. People do not intentionally act in accordance with things they do not believe to be the case. To accept determinism without fully processing the implications thereof, particularly if it "feels wrong but seems true" is to enter into and sign up for those internal conflicts writ large in one's own life.

I also don't believe that the universe is absolutely deterministic, but that's a different argument that others have made better than I likely would.