Shaikh Saaleh Al-Fawzaan (may Allaah preserve him) said:
It is not permissible to exalt and praise the innovators even if they have some truth with them. That is because raising and praising them will spread their bidah and places them amongst the sincere ones-those who are taken as examples amongst distinguished men of this Ummah. The Salaf warned against having trust for the innovators; (warned against) praising them and their gatherings. In this regard, Asad Ibn Musa (rahimahullaah) wrote: ”Beware of being a brother of the innovator (by association) or a companion of his, or one whom you sit with. For indeed it has been narrated that ‘whoever sits with a person of innovation has left the protection of Allaah and is entrusted to himself. Whoever proceeds towards a person of innovation has proceeded towards the destruction of Islaam.”
The innovators must be warned against and kept away from even if they have some truth with them. Indeed, the most astray are not devoid of something of the truth, but as long as they have with them innovation, opposition and sinful views, it is not permissible to praise and exalt them. It is impermissible to not have an objection towards their innovation because in this is spreading of bidah and belittling the Sunnah; and through this the innovator will emerge and become a guide for the Ummah.
As for the consideration that he has something of the truth, this does not justify praising him. This is to a far greater extent against that which is of overriding benefit and it is known with regards to a principle of the religion that averting harm takes precedence over seeking that which is of benefit. And with regards to showing animosity towards the innovator, the harm that is averted from the Ummah is weightier than what he has of benefit. And had we adhered to this concept, no one would have been judged to be misguided and declared an innovator. This is because there is not an innovator except that he has with him some of that which is from the truth and adherence to the Sunnah. The innovator (may) neither be a disbeliever nor is he in opposition to all the Islamic legislation; rather he is either an innovator in some or most of the affairs. However, if the innovation is particularly to do with affairs of Creed and Methodology, then the affair is dangerous indeed- because it will become example (to follow); innovation will spread and the innovators will become active in spreading their innovation.
So, this one- who praises the innovators and makes their affair obscure to the people with what they (innovators) have with them of truth- is one of two (people): He is either one ignorant of the methodology of the pious predecessors and their stance against the innovators, and it is neither permissible for this ignorant one to speak nor is it permissible for the Muslims to listen to him; or he is one who has an objection to the truth because he knows the danger of innovation and the innovators, but he is one who has an objection and wishes to spread innovations. Nevertheless, this is a dangerous affair and it is not permissible to be lackadaisical with regards to innovation and its people, whatever that may be. [Source: At-Tabdee Wat-Tafseeq Wat Takfeer. Page: 72-76. Abridged and slightly paraphrased]