Pick out one or two behaviors on which you want to start (talking back to adults, for example). Sit down with your sons and explain that you are going to start focusing on times that they talk appropriately with adults. Put a chart in a very obvious place (the door of your refrigerator, perhaps) so that you can keep track of the times when they answer adults appropriately.
Put a check mark or a sticker on the chart each time one of your sons talks appropriately with an adult. You can use different colors of marker or stickers for each son so that you can keep up with the behavior of each. Decide on the goal for earning a reward; you may want to start small, with one sticker or check earning computer or TV time. Three stickers in one week can earn having a friend over to play on the weekend. You can increase the number of stickers or checks required to earn a reward as your sons' behavior improves.
The key to any system like this is to use it consistently, giving a check or sticker every time they talk appropriately, and over a long period of time. This is not something to try for a week and then give up. Check your public library or a bookstore for a book on positive discipline -- you can get other ideas on dealing with your sons' behavior. It sounds like your sons may be pushing your buttons when they say you don't love them. They know that you do, and they also know that it upsets you when they say that. Don't argue with them when they tell you that you don't love them; try to ignore it and walk away. Show them that you love them with hugs and positive consequences when they are doing what you expect.