John Scalzi's posted ten points about free speech, conversation, debate and related subjects. There's lots of good stuff there: "8. If people do not engage you, it is not necessarily because they are afraid to engage you. Maybe they don't have the time, or interest. Maybe they think you're too ignorant to engage, either on the specific topic or in matters of rhetoric. Maybe they don't want to either implicity or explicitly let you share in their credibility. Maybe they think you're an asshole, and want nothing to do with you. Maybe it's combination of some or all of the above. They may or may not tell you why."
1. As a general concept, freedom of speech includes the right to decide how and when to speak, and to whom.
2. This freedom of speech also includes the right to choose not to speak, and not to speak to whomever, including to you.
3. No one is obliged to have a conversation with you.
4. If they are having a conversation with you, they are not obliged to give you the conversation you wanted or expected to have.