First, don't respond to HR with a complex set of legal questions. They wont know the answer and will push back -- corporate attorneys will charge astronomical amounts and these questions could even get the board involved -- which the CEO usually doesn't want to do.
My suggestions:
1) The strike: Print the document, strike out what you don't want. Scan it, return it to the HR dept. with, "Hey cool signed!". Only do this if you are pretty senior.
2) The re-write: Take the document rewrite it, with the statements you don't like removed, then return it to HR with, "Hey cool signed!"
3) The 'it is coming!' (for junior guys):
Take the email and delete it. Say you never got it. They will resend it, take it and place it into your spam folder, two weeks later say you never got it. Then reply back with your w9 two weeks later. Then if they complain reply with a w9 3 weeks later. Continue until you have clout then do 1 or 2.