You grossly misunderstand the concept of creating a political party. You have a core that have the same ideals and ideas. You create the party. If people agree with these ideals then they then join the party too.
People have the choice. If they dont like the views of a particular political party then they simply do not join it.
Simple
Going along the lines of this hypothetical proposition of a BL political party, we're not saying that everyone on BL has to agree. Simply that it was formed by people of BL.