All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
We advise you to ask about Islamic knowledge that you need and avoid asking questions that will not benefit you in your religion.
As for declaring specific Muslims who show the rites of Islam that they are non-Muslims, then there is no benefit in it. The general principle is that a Muslim remains a Muslim unless it is proven with certainty that he is a non-Muslim, and the conditions of Takfeer (i.e. declaring him as a non-Muslim) apply to him while there are no impediments that prevent from declaring him as such.
It is only the Islamic judiciary that may do so, or those who may act instead of it, such as Iftaa’ Committees, or great scholars who are known to make Ijtihaad.
The scholars have extensively elaborated and had great debate on the case of Abu Hayyaan at-Tawheedi and his ideology, and there is no need for us to indulge in it.
For more benefit, please refer to Fataawa 289150, 91372, and 335743.
Allah knows best.