Hate to burst your bubble, but Pentecostals are clearly part of the Protestant constellation of sects.
Much in the same way splinter orders of lesbian militant communist nuns are part of the Catholic Church?
When you paint with a broad brush you tend to get some on yourself.
In Catholicism, its clear that lesbian militant communist nuns are dissenters who disagree with their Church's teachings. The Vatican appoints overseers to their representative bodies to make sure they change their beliefs to return to full communion. Fortunately these obvious dissenters represent a tiny fraction of Catholics.
Pentecostalism, on the other hand, is one of the largest and fastest growing bodies of Protestantism, and mainstream Protestantism has no mechanism to check and correct their errors.