1.) Your first argument is invalid.: what
some people who
claim to be members of a group, say or do, in no way reflects on the entire group. Besides, I would say that those people are certainly not Christians. In any case, their actions are immoral and illogical: how can you make a stand against the murder (of babies) by committing murder (of adults)? So, I hope we've left this argument to rest.
2.) David Koresh was not a Christian. In fact, he claimed to BE Christ/God. So that would make him an ANTI-Christ. Also, he encouraged things like polygamy, arms stockpiling, etc.... things that Jesus didn't really support.
3.) The Christian movement was NOT originally violent. Read any of Jesus' words or Pauls' writings, and NONE of them encourage violence. In fact, Christians were the victims of violence. In the first several HUNDRED years during and after Christ's life, Christians were persecuted by both Jews and Romans, the former accusing of sacrilege and blasphemy, the latter of insubordination to the state. They were crucified, beheaded, blamed for the fire of Rome in 64 A.D., fed to animals in the circuses, etc. So your argument falls flat there too.
4.) I repeat my argument, it is possible to witness to a person in a loving, dignified, and tactful way. That is the way I advocate and intend to employ, Godwilling.