Dear Qwerty,
It is not clear to what extent these “certain Chabad beliefs are heretical”. There is no obligation on Jews to master philosophy. If people have irrational beliefs, than so be it. There isn’t any more harm in their carrying these beliefs into Judaism. Wise people will always spot the fool. If you are talking about across the board Chabad beliefs, then you will win this argument only when you are able to talk for everyone. Those who understand how Chabad thinks within their system, are aware of how it is solely based in known and authenticated Chassidus. If you really learn Chassidus well, much of what bothers you will fall away.