Any ideas for why that email appeared in your inbox? It doesn't look like it's a phishing attack - "Updates to YouTube's Terms of Service" is a subject line that guarantees that precisely zero people will even bother opening it.
If I click unsubscribe, and the form asks me to fill in information, it gets marked as spam. No, I'm not filling in my email, let alone completing a CAPTCHA, to ask you to stop sending me emails.
However, I don't click an unsubscribe link in an email where I suspect the unsubscribe link is itself a scam to collect information.