Compared to other online communication forms, forums tend to bring out the worst in people, especially when discussing politics and other controversial topics. Otherwise reasonable people can become screaming banshees.
You can contact your elected representatives by email, though of course their staff will handle it. Whatever opinion you express will be tallied with similar opinions on the subject. However, I have heard that mailed letters carry more weight in the tally because there is the additional cost of postage, which requires some extra dedication (i.e., a sign that you might do something about your opinion, such as change your vote, participate in a mass protest, give a campaign contribution, etc.).