Is it correct to say that shirk (polytheism) and kufr (disbelief) can't be actions, because they are beliefs and not deeds?
Can you please explain?
Actions and words may be irrefutable proof of a person's beliefs i.e. his actions are the manifest proof his creed or they may only be probable. However, a person's actions and words may probably denote disbelief. It is incumbent to construe the actions of a Muslim in the best light. Hence, it is impermissible to accuse another of disbelief as long as an action may be either interpreted positively or there is an excuse for it. For instance, prostrating before another may be a form of greeting like the prostration of Prophet Yusuf's brothers before him or it may be a means of worship like that practiced by the idolaters. It is impermissible to interpret prostration negatively even though all forms of prostration are prohibited in Islam.