The excuse "you allowed it because you didn't do the custom install" is debatable since it's arguably true that even if you didn't read the pages of agreement, you would not reasonably expect Avast to modify your computer with non-AV stuff.
This isn't the first intrusion like this from Avast and when my computer (Winpatrol?) told me Avast was trying to install SafePrice, I denied it, removed Avast, and installed Avira Free - which actually scored better at AV-Comparatives on the latest 166,522 virus study in detection, removal, and speed. Either one is a great AV and I'll go with whichever one asks before it installs stuff. Avira's Browser Safety extension includes a price comparison tool, but you can turn it off.
Thanks, Avast, for a great, free AV product, but when you started messing with non-AV-related stuff on my computer without at least informing me you were going to do it, it made me feel like you wanted to force certain PUP's on me before you'd clean others.