Qadiyani Sect
There are many other sects too, who are preaching misconception..The greatest one is preaching and justifying polytheism in Islam. They preach that the prophet and the saints have divine attributes, they offer sacrifices and distribute food in their name and at shrines, which is an explicit shirk. One should be more sensitive to them as the greatest sin is polytheism. If you feel you need to counter these and other wrong doctrines among the Muslims, that is appreciable. For this purpose, you need to educate yourself in the subjects at a good scholarly level, af the first place and then set up a well-informed counter-narrative.