I would say yes. Passivity shows disrespect for yourself and allows others to run over you for the sake of avoiding conflicts. Aggression also stems from lack of self-esteem, as when people disrespect and run over other people, they are trying to force their way, probably because they don't believe they can get their needs met any other way.

Assertiveness is based on believing that what you feel, think, and need has merit enough to be presented clearly and directly, and enough self-esteem to consider what others need/think/feel also and work out a solution that works best for both of you.