Sheikh `Abd al-Wahhâb al-Turayrî, former professor at al-Imâm University in Riyadh
The term Shî`ah applies to numerous sects throughout history that had a wide spectrum of beliefs and teachings. Therefore, we cannot say that all the Shî`ah are unbelievers.
On the other hand, there are many sects of the Shî`ah who advance claims that are tantamount to unbelief. Anyone who believes such things would be an unbeliever, whether or not he claims to belong to the Shî`ah.
For example, anyone who accuses the Companions of hypocrisy while the Qur’ân tells us they are believers and Allah is pleased with them is an unbeliever. Allah says: “Allah’s good pleasure was on the believers when they swore fealty to you under the tree”.
Likewise, whoever slanders `A’ishah is an unbeliever and rejects the sacred text, the Qur’ân, that attestss to her innocence. Such slander also derogates the prophecy.
Those who say that the Qur’ân has been corrupted is indeed rejecting Islam.
There are many other deviant acts and beliefs associated with various Shî`ah sects that do not constitute unbelief, so no one can claim that the adherents of all the various Shî`ah sects are unbelievers.
May Allah guide you.
Source: Islam Today