Inn The Name of Allaah, The Most Merciful, The Bestower of Mercy
Whoever does not make Tabdee of a Mubtadi is himself a Mubtadi!
Shaikh Rabee [may Allaah preserve him] stated:
It is not correct to apply this principle unrestrictedly because it maybe that he is unaware of the Bidah committed by that person, therefore he refrains from declaring him an innovator due to Wara [apprehensive fear].  Why should you declare him an innovator? [i.e. why should you declare him an innovator when it is the case that he is unaware of the bidah of that Mubtadi or refrains from making Tabdee out of apprehensive fear].
But if he knows the innovator, [i.e. knows that such a person is upon bidah due to which the evidence was established against him], loves him and allies with him, then he is a Mubtadi. This is the distinction in this affair – he knows that that person is a Mubtadi but he aids him and wages war against Ahlus Sunnah Wal Jamaa’ah, then he is a mubtadi without a doubt. As for a person who does not know that such and such person is a Mubtadi, he is not to be declared an innovator.
[As for] you [i.e. the scholar or student of knowledge who is qualified to make Tabdee] – the one who studied the affair of [that person] and you know that he allies with a Mubtadi, puts him in a favourable position, wages war against Ahlus Sunnah for the sake of that Mubtadi and for the sake of this falsehood, this person is a Mubtadi; misguided.
As for the person who does not know that indeed such and such person is a mubtadi, then advise him and clarify for him [i.e. with clear unambiguous proofs until he understands] that such person is a mubtadi. So unless he ceases [i.e. refrains from defending this mubtadi after understanding the evidences], then put him with his companion – the mubtadi. [Source: Awnul Baari 2/891..slightly paraphrased & abridged]
Translation of the tern [Al-Wara -Apprehensive fear] was taken from one of Ustaadh Amjad Rafiq’s [may Allaah preserve him] articles.