In fact he frightens us with a warning, at the same time very compassionately. It is not just a false warning; it will surely happen that way. We should not allow it to happen.
We have to develop an unshakeable faith in the thought ‘I have come to this Guru. Let him appear to others in whatever way they think. As far as I am concerned, God will not let me down; He will certainly grace me, through this Guru, with the Release that I seek’.
The conviction and faith that we usually develop in our Vidya-Guru (the teacher who instructs us with the basics of education) in our early days, -- that same conviction and faith has to be there in the dikshA-guru (the Guru who finally grants us the sannyAsa status). It is important to cultivate this shraddhA-cum-bhakti-cum-sharaNAgati.
Of course it is true that one should resort to a guru only after thorough enquiries about him. But suppose you land yourself with a fake guru. Even then, if without losing faith in him, if you surrender to him, the All-knowing Lord will bless you with Enlightenment through that Guru, though he may not himself be a JnAni!
“Conviction comes only by actual perception by ourselves as truth; instead of this if one goes on faith by the shAstras and the Acharyas who repeat those shAstraic statements, that cannot give a firm conviction” – such thinking is nothing but absence of shraddhA.
On the other hand shraddhA is the faith that says: “By the very fact that something is not comprehensible to my little intellect it must be higher than what can be revealed by my own inquiry; it must be the truth revealed to the Rishis and passed on to us by the Shastras”.