Standing up for your significant other is one of the most important things in a relationship, besides love & trust. If you're not willing to put family, friends, or anyone else in their place for downing, insulting, or disrespecting your spouse, you shouldn't be with them in the first place.
Relationships & marriages are a team effort. If someone talks bad about your spouse to you, them or anyone else, you should take offense to it because they're also insulting you!
Maybe I'm a different breed, but I feel like more people need to hear and understand this.