What's your opinion about this?

You and your husband are a team - in a situation like this I feel that it is something both you and your husband MUST agree on. If you do not agree then your husband's friend should not be staying in your house - You and his children should always come first and it does not seem that this is how he is handling it. Also he is the one that should tell him and not make you look like the bad one. This is not a good environment for your children (drugs and booze).