But, I also found ton of videos or forum posts, who made harsh critics about ninjutsu teacher on the internet, mocking them and showing that they were fraud.
Now, I'm asking, are all the ninjutsu fraudulent like said in these videos or the reality is more shady?
I don't know what videos or forums you've been looking at, but I suspect you may be conflating some very different criticisms of different teachers.
One category of criticism is that someone is a literal fraud, meaning they are deliberately, knowingly deceiving students about the material they are teaching and their qualifications for teaching it. This would cover teachers who claim to have learned an actual historical Japanese lineage of an art practiced by the historical ninja directly from the last surviving member of a ninja family, when in reality they just made it all up based on a foundation of karate and inspiration from movies. (Since MartialTalk has a prohibition on fraudbusting, I will not be naming any names.) These individuals may or may not be competent martial artists or instructors, but they are frauds in that they are lying to their students.
The next category would be instructors who learned from the first category (deliberate fraud), but who believed what they were taught. These individuals may or may not be competent martial artists or instructors, but their art has no connection to historical ninjutsu. I would not call these teachers frauds, although they may be misguided.
The X-kan (Bujinkan and its offshoots) arts occupy an ambiguous place in relation to the categories above. The arts taught in the X-kan organizations include modern interpretations of genuine verifiable historical Japanese arts. However the verifiable arts are not ninjutsu and the ninjutsu arts are not currently verifiable as being genuine historical arts reaching back to the actual ninja. There are practitioners doing research in verifying such a connection, but it may never be proved one way or another.
If the "ninjutsu" components of the X-Kans
were created fraudulently, it would have been done over 60 years ago, by someone who at least had a solid foundation in historical Japanese arts and may have been attempting to recreate a ninjutsu system based on that knowledge. In any case, current practitioners of the X-Kan arts should
not be regarded as frauds in the sense of deliberately misrepresenting themselves or the history of their art. (Unless you find an instructor who lies about his rank or training, but you can find that sort of thing in any art.)
The other sort of criticism you might encounter is the idea that the training in "ninjutsu" schools (Bujinkan or otherwise) is just not effective for the claimed purpose of combat or self-defense and that the instructors are "fraudulent" for claiming it is. Whatever the merits of such criticism, I would argue that "fraud" is the wrong word. Every "ninjutsu" instructor I have ever met or trained with has been genuinely confident in the value and effectiveness of what they are teaching. If they are wrong, it doesn't make them frauds, just misguided.
I should add that every single martial art on the face of the planet has detractors who will claim it is ineffective for self-defense. Until you have personal experience, you don't have a good basis for knowing which critiques have validity. I spent a number of years training in the Bujinkan before I went on to other arts. I have my own opinions and critiques of how they do things. However since you've never met me or trained with me, you have no way of knowing whether my opinions are worth anything or if they're a bunch of hot air. If you are interested in the Bujinkan and have a good school nearby, give it a try and judge for yourself. (I should warn you that the Bujinkan does have a well-deserved reputation for … inconsistency in quality control when awarding rankings. If the teacher you find has a high rank, they might be really good ,,, or pretty crappy … or somewhere in-between. Caveat emptor.)
