One thing we need to be aware of when discussing social issues is the concept of intersectionality. This concept details that all kinds of oppression are related. Sexism, racism, ableism, classism, etc are all products of systematic oppression. Resolving one of these issues does not resolve all issues of oppression, it only redirects the problem.
For example, a few months ago gay marriage was legalized. While this was an amazing step forward, it doesn't detract from the fact that trans people face so much discrimination. To give you an idea, 41% of trans people have said they've attempted suicide compared to the 1.8% of the general population. This is a direct correlation with the fact that they are unemployed half as often as the general population, are four times as likely to have a household income of less than 10,000, and one in five trans people face homelessness. Not only that, but over half of homeless trans people said that they were harassed at the homeless shelters by other homeless people and the staff, a third said they were turned away altogether and nearly a quarter were sexually assaulted. They face housing discrimination, arbitrary evictions, and healthcare discrimination. These numbers haven't changed since the legalization of gay marriage and aren't expected to change unless something is actively done about it.
What do these issues have to do with interpersonal communication? Interpersonal communication has to do with exchanging information, feelings and meaning through verbal and nonverbal messages. While it doesn't take the place of educating yourself and taking a stance against social injustices, I believe that understanding communication can make you a better ally. Again, using the previous example, if you know a trans person who was born with the physical anatomy of a male, but now prefers female pronouns. In using male pronouns in this case, you are saying "I understand this issue better than you do", "your concept of self isn't respectable, real or important". and "my comfort and familiarity is more important than your sense of self." Communication send important information beyond just what is being said, especially for issues as sensitive as social issues.