Taken from the watchtower's own words: http://www.jw.org/en/publications/magazines/g201306/the-silent-treatment/
"when it is used as a means to retaliate or manipulate, the silent treatment not only prolongs conflict but also erodes [...] respect"
The silent treatment between spouses is directly condemned by the article as unloving, unproductive, retaliatory and manipulative. Just because you might not be married to someone doesn't make this behavior any better or somehow loving all of a sudden. In fact, I would argue that participating in the systematic and indefinite "silent treatment" of shunning is far worse than giving a spouse the silent treatment for a few days.