Uninstalling Avast - breach of customer trust

I've been using Avast antivirus for quite a while. Today I noticed that it started adding an email signature to my outgoing gmail with an ad and link for Avast! Without my consent or telling me! Holy Schnikeys! That's a complete and total breach of trust. What genius at Avast thought it is a good idea to modify a customer's email?!  I'm uninstalling it now.