I don't understand when you say landing page because landing page can mean a lot of things, but I'll assume you're talking about a blog post.
To answer your question:
It all boils down to user experience, if Google is sending you traffic and people keep hitting the back button after visiting your page then you'll drop in the rankings. Some people will hit the back button simply because they can't find a way to close the Advert, whether on desktop, tablet or mobile phone these Ads can be tricky sometimes.
Another reason would be someone on a really slow internet connection, or someone who uses data bundles (capped internet). These 2 type of people will hit the back button as fast as they came in when they can't see what they came for.
So your friend is right, it will affect your bounce rate then end up affecting your rankings.
In conclusion, I would look at this from the end user's standpoint to see if it benefits them or not, to make sure that the Ads are not a destruction for the end user.
That's just my 2 cents, I never use pop-ups or pop-under Ads on my blogs because I hate seeing one when I visit other people's blogs and sometimes it's just annoying and I close the page as fast as I came in then search somewhere else.
