Is smiling in the face of an innovator (Mubtadi') considered disbelief (Kufr) if the innovation is a major one (Mukaffirah), and is loving an innovator disbelief?

The summary of the answer: The words attributed to Al-Fudhayl ibn 'Iyad regarding the condemnation of innovations (bid'ah) and their practitioners are for emphasis and warning, not a ruling of disbelief (kufr) or nullification of deeds for specific individuals who commit them, as such rulings require textual evidence from Islamic law. Sheikh Nasser Al-'Aql has pointed out that some of Al-Fudhayl's expressions are questionable, such as specifying a reward of "one hundred degrees," because the specification of such matters is توقيفي (requiring divine textual evidence), and their issuance from Al-Fudhayl does not mean their acceptance in every aspect. As for Fatwa no. 114610, it does not prohibit smiling in the face of a disbeliever without necessity or affection for his person. Rather, it permits natural affection for a non-belligerent disbeliever for reasons such as kinship or good character, and it permits laughing and smiling in the face of a disbeliever. This also applies to loving a person who commits an innovation that amounts to disbelief (bid'ah mukaffirah) with natural affection due to kinship or kindness; this is not disbelief or sin, unlike loving him for his innovation. Therefore, merely smiling in the face of a person who commits an innovation that amounts to disbelief is neither disbelief nor a sin.