Shared use of the backcountry demands cooperation between different user groups. Sooner or later, you'll have to meet with representatives of other outdoor groups. Some members of these groups may be completely hostile to mountain bicyclists. Most members will be curious or worried about the impact of mountain biking. Establish your legitimacy, your commonality, and your willingness to work together.
Individuals resist change and are suspicious of strangers.
Try to find mountain bicyclists within the other groups and encourage them to get involved. Join the groups if it is appropriate. Work from within. Work with other groups in trail building and maintenance, political lobbying, and other environmental efforts. Show them that mountain bicyclists appreciate the backcountry for the same reasons they do, follow the IMBA Rules of the Trail and practice the Leave No Trace philosophy.