The problem isn’t that avast is using ads to finance it’s free version. I’m kind of fine with that.

The problem IS that avast quite literally monitors what websites you visit and tailors it’s ads by preying on your fears.

“Be afraid, someone could be looking at your porn habits right now just like we are. Give us money to prevent others from dong exactly what we are doing.”

It’s not much more than a hop, skip and a jump from here to being no better than the blackmail trojans they purport to protect you against!
I don’t want anyone to spy on me, and that includes the people protecting me from being spied upon.