why not religionism ?

[Irreligious Atheist]

Onto Sungula's point, I do agree with him that people here don't seem to take anti-Muslim bigotry serious enough, and seem to dismiss it sometimes, just because they don't like the Muslim poster WinterHold or whatever,

This forum does take it seriously. We simply don't take Winter seriously because he's a tool.

but at the same time, Muslim apologists do call people Islamaphobic just for criticizing Islam. 

This rarely ever happens in contrast to people cloaking their bigotry in criticisms of Islam, And is not a valid reason to reject a term.

Therefore, it only makes sense that we use a different term for criticism of Islam, than the term used for bigotry against Muslims.

Nope, it doesn't make any sense at all. Because some people on ultra-rare occasions have misused a term does not mean a different term should be used. That's absurd. By that logic, Antisemitism should be abandoned because the pro-Israeli group has abused to silence critics. That doesn't change the fact it's a legitimate term that accurately describes a phenomenon.

 Islamaphobia is a sneaky term used to prop up Islam in some instances, so I reject the term.

Virtually never and that's a really silly reason to reject a valid term.

https://www.lexico.com/en/definition/Islamophobia

Islamophobia - Dislike of or prejudice against Islam or Muslims, especially as a political force.

https://en.wikipedia.org/wiki/Islamophobia

It is attested in English as early as 1923[27] to quote the French word islamophobie, found in a thesis published by Alain Quellien in 1910 to describe a "a prejudice against Islam that is widespread among the peoples of Western and Christian civilization".[28]

The term did not exist in the Muslim world,[a] and was later translated in the 1990s as ruhāb al-islām (رهاب الاسلام) in Arabic, literally "phobia of Islam".[28]