if you're using Chrome, go to your preferences and near the top, there's "Sync and Google services". within that is an option to send URLs you visit to Google. turn it off if it isn't already.
regardless of browser, if you have a Google account (such as for GMail) that you're signed into in the same browser(s) that you're using for YouTube and other things, go to your Google account settings (https://myaccount.google.com/), click "privacy and personalization", scroll to the bottom, and turn off ad personalization.
this should make your ads more random. if you're still getting harassed by Xero, then it's their fault.