Well, first of all, when he is right about what those wrongs we have committed, don’t disagree with him. It is a scandal what we have done to those we perceive as “other”, even though it may fairly be said that nearly every other culture, religious or not, has eventually done the same thing when the opportunity presented itself. Their golden ages of tolerance have come, yes, but they’ve also gone at times, too. The Church has not always gone any further beyond our fallen human nature than anyone else. This does not, however, mean that he needs to be allowed to get away with some romantic nonsense about the “old” religions acting any differently. A survey of their pasts will quickly uncover its share of bloodied hands.
Also, remember that some offenses taken as personal by pagans were not actually perpetrated on the pagans themselves. They were perpetrated against Christians that others in their group imagined were pagans! In the Salem witchcraft trials, for instance…as nearly as I can tell, no actual pagans were sacrificed. The victims were Christians who had been subjected to smear campaigns. Now there are modern pagans, people who are practicing a religion that was made up within the last century, taking these tragic incidents within some small Protestant sect as a personal attack on them by the Catholic Church…a Church that was also under attack by some Protestant groups as being pagan and false herself!
Also, if you go back to Greece and Rome, you’ll find that pagans didn’t have much problem with sacrificing Christians for sport, when it was the pagans who had the upper hand. Shall we, then, blame modern-day pagans for the sins of powerful people to whom they have mere paganism as a relation? Well, why not, when modern-day pagans have no problem with taking Christian atrocities that had nothing to do with them as personal affronts?
As far as “stealing” pagan practice, why is it theft when your converts bring their old practices with them and you allow them to combine them with yours? If that weren’t done–not that there was much choice in many circumstances!–we’d have been accused of abusing the converts by robbing them of their culture!
IOW, we need to admit that we often fall short of our own ideals, but those who accuse us also need to take care that they aren’t trying to have it both ways themselves.
It does not hurt to know that pagans have their own moral code. The first is the three-fold rule: What you send out into the world will re-visit you threefold. Therefore, if your brother is sending venom towards Christians out into the world, he has to remember that by his own religion, that venom will one day come back three times as potent to bite him. Their other rule is this: Do no one harm, then do as you will. You may call this a pale imitation of the Golden Rule, and I won’t argue that it isn’t, but it is the rule that binds him. If he seeks to do harm to you, he is in violation of his own morality.
Be certain in all this that you follow the Golden Rule: Do unto him as you would have him do unto you. I think we would all agree that we would want to be loved, we would want to be given the impression that the other person was making an effort to understand us where we were, and that we would want them to keep trying to bring us back around to the truth. As you do so, remind him that you cannot keep yourself from giving him the best that you have to offer. If he doesn’t like the gift, ask him to please at least accept it with the sentiment intended. Try to accept what good he attempts to send you in the same spirit.
If you want to find out more about what wiccans believe (which comes in about as many different forms as there are wiccans), you might go to your local library to see if they have something like “When Someone You Love is Wiccan”. When you’ve done your homework about them, you’ll have won yourself that much credibility, at any rate, and maybe some compassion, too.
If he launches into a pagan story for your benefit, act interested, even fascinated and thank him for sharing–then be prepared with one of your own Christian tales to tell in return. It will take the wind out of his sails if he can’t get under your skin or get you to argue with him.