Words have power. Words have the power to diminish, uplift, accept, exclude, validate, believe, and diminish. Gender pronouns, in this way, express respect for someone's gender identity and shape the way we approach gender relations.
Failing to respect folk's gender identity is not only harmful, it is oppressive.
Embracing folks' gender pronouns and approaching normative pronouns with caution is an important step in countering rape culture and sexual violence. Sexual violence is often used as an excuse to "fix" those who don't ascribe to a cis/heteronormative framework of identity and sexuality. By respecting folks' gender pronouns and using them confidently, we assert respect for their humanity.
For a guide on pronouns please consider this valuable resource from the University of Wisconsin Milwaukee LGBT Resource Center.