"Honesty is important in our information and approach. This can be difficult, because in today's society, it seems that if we don't scream the loudest, we're not heard. Because moderate voices are often drowned out, there can be pressure to exaggerate claims in order to advance our cause and to counter those who lie to defend the status quo. Furthermore, there's a natural tendency to accept any claim we want to believe without critical examination. This can be especially true of vegetarians, who often feel isolated in a meat-eating world. In the long run, however, being uncritical in the information we believe and use for advocacy can harm our efforts, because we lose support from people who have come to realize that we're not objective, and we miss chances to convince people who are inherently skeptical.
More importantly, meat eaters are looking for some reason to dismiss new and potentially inconvenient truths--few people want to face the suffering in the world, let alone make real changes in their lives. If we offer them one morsel of questionable information among our sea of facts, they will seize on that to write off everything we say as suspect. It is imperative we present information the public can't disregard from sources they can't dismiss."
From The Animal Activist's Handbook by Matt Ball and Bruce Friedrich