Communications Solely With Google. You agree to direct to Google, and not to any advertiser, any communication regarding any Ad(s) or Link(s) displayed in connection with Your Property(ies).
In this context, I believe it is the advertiser who is in violation. lappert2001 was contacted by the advertiser, not the other way around.
IMHO, I would notify Google of the contact. It is not worth jeopardizing a long term relationship for a short term gain. Who is to say the advertiser would not bail on you as they are obviously willing to bail on Google. Then what do you do?