It seems rather pointless to come into a 'vajrayana' forum saying such things like in my opinion a guru is not necessary for liberation ' When in Vajryana it is.
Strictly speaking, liberation from suffering is not the same as buddhahood. The point of Vajrayana is rapid progress to buddhahood.
My point really is that it is perhaps wiser to achieve liberation from suffering (particularly neurosis of all types, including emotional reactions) first and then think about buddhahood. The former does not require unconditional faith in a guru, and if you have achieved such liberation, then you'll be in a ready state to truly discern who is and is not a qualified guru.
I say this out of concern because, frankly, I've met a lot of people who strongly advocate Vajrayana on one hand yet display instability in their lives, particularly with respect to their emotions, relationships and life decisions. The numerous charlatan gurus don't help much.
We frequently hear Vajrayana teachers speak of "suitable vessels". Well, if general conduct and stability are any guide to suitable vessels, I don't see a lot of practitioners displaying the requisite qualities.
I also wonder where all these realized beings are in organizations that display strong nepotism and coverups of scandals. Sexual abuse in Tibetan monasteries is a real concern, so if the enlightenment machine really works so well, where are the bodhisattvas and realized yogis addressing or better yet preventing these problems?
I sincerely think focusing on the basics and foundations before proceeding to lofty goals of buddhahood is needed. It eliminates the widespread need for gurus, which would curtail a lot of the abuse in my estimation. If turbulent passions are placated as the Buddha taught, then a clear mind and firm foundations will ensure people can make good decisions with respect to their relationships with others.