Associating partners with God, declaring takfir

[Sleepysoul]

Salamun' Alaykum.

I wanted to know if you think it's okay to say/assume that some (or all) Sunnis/Ahl-Sunnah/Salafi are 'unknowingly' associating partners with God? This partner being Prophet Muhammad (pbuh). The way they hold his alleged words so highly alongside Allah's and in cases I'd say even more than Allah's perhaps. Or is pointing something like this out akin to 'takfir'? Also, I'm assuming it's a sin to declare 'takfir' on someone?

I recently suggested to a 'Muslim' to read the Qur'an without tafseer/Hadith and that he may be surprised, his response was that he would be deluded if he did that. Basically, Allah's words would delude him if he didn't read them with support from Hadith. He said the Qur'an itself says it will delude you in Surah Baqarah. I don't know what he was talking about there.