You can unite martial artists when they are under your roof. Be cool to people and develope your own reputation. Practitioners of many styles have visited our dojo; We even share space with two TKD schools! We're not interested in the politics of other aikido dojo. We get along at our school, and when we visit other schools. If people are too judgemental and combative, they're crossed off the friend list.
Love all the martial arts, and they'll be united in you. Teach others your way of thinking, and you've got a good start.