Consumer goods are produced when you have industry infrastructure build on your planets. To make consumer goods you also need raw material. You have to know that only for Aspha Miners it`s really profitable to produce consumer goods, all other races should just buy them on the market. You`ll automatically sell consumer goods for 5$ to your population when you use a turn.
When you plunder a colony you won`t lose loyalty on other planets or experience any other negative effects. You just lose the colony and your planet count will go down, that`s it. I don`t know if you experienced that your loyalty went down, but if you did you probably didn`t have enough food to feed your population. When there`s no food left your pop will starve and loyalty will drop, so make sure you buy/produce enough food.
Enjoy the game!