I don't know what Rav Elon did, if anything. I trust the signatories of the letter (a very diverse and extremely well respected group of mainstream Religious Zionist leaders, including Rav Lichtenstein and Rav Ariel). I do not know if Rav Elon is a criminal, a sinner, or none of the above.
I do know that Rav Elon is extremely charismatic, and I do not trust charismatic rabbis. Not a single one. Moreover, I believe that God does not like charismatic teaching, and that this is His critique of Eliyahu ha-Navi in Melachim I:19 - the path to God does not lie in earthquake, wind, and fire, but in the still, small voice. And the path to God never, ever, leads through an individual human being. Long time readers of this blog know that this is a theme that I have often returned to. (for example, see here, here, here, and here, among other places).
An excellent (but somewhat different in that it relates specifically to the high school milieu) articulation of this mistrust appears in a recently published book by Paul Shaviv called The Jewish High School: A Complete Management Guide; Leadership, Policy and Operations for Principals, Administrators and Lay Leaders. He has a section entitled "The Charismatic Teacher" that he actually posted in a comment over at Hirhurim about 4 years ago. It is in the public domain (here), but I'll reproduce the relevant sections here anyway. [Update: as the author notes in the comments, the print version of the text differs from the version below. He has posted the entire passage, as it appears in the book, here]:
The charismatic teacher (the ‘Pied-Piper’) is one of the most difficult situations for a Principal to deal with. A charismatic teacher will deeply affect and influence some students, but will almost always leave a trail of emotional wreckage in is/her wake .Buy the book if you want to read more. And thanks, AB, for this link.
Charismatic teachers are often themselves deeply immature, but their immaturity is emotional, not intellectual, and it is not always obvious. They can be brilliant in inspiring students to go beyond their wildest expectations, and are often regarded (by their following of students, by parents, and by the Board or the community) as the ‘most important’ or ‘best’ members of staff. There is always, however, a price to be paid. One of the effects of charisma is to convince the recipient that he or she is the centre of the charismatic personality’s concern. A teenage student (or a particular class) may feel as though he or she is the protégé of the charismatic teacher. The moment they realize that they are not (sometimes when the teacher ‘moves on to the next’), deep emotions come into play. In the same way, many charismatic teachers will lavish attention on a student or group of students as long as the student(s) do things the teacher’s way, or accept every piece of advice or ‘philosophy’ or Torah uncritically. The moment the student shows independence or objectivity, they are dropped. As soon as they are disillusioned or dropped, they are written out of the teacher’s story. Often such students, very hurt, leave the school. Mild characteristics of cult leaders may be observed.
Other parents, however, will rave about how their son/daughter ‘adores’ Mr./Ms/ or Rabbi X, and is learning ‘so much from them’. Events linked to that teacher will be showcase events, and in certain cases the Principal (or Head of Department) will come to be dependent on the teacher. ‘We need something special for the prize-giving...or the ground-breaking … or the community event… can you put something together?’ The teacher will protest that the time is short, and it’s impossible, but will, of course, accept and do a fabulous job.
The problem is that at core, these are not educational relationships. The emotional dependency and entanglement between teacher and student leads to boundaries being crossed. The teacher throws open his/her house to the students. Teens idolize the teacher, and fantasies begin to develop. The charismatic teacher will solve the teen’s angst and will sympathize with their intimate family problems. The teacher becomes party to knowledge about students and their families that reinforces the teacher’s view that they are the only teachers who ‘really’ are reaching the students. The teacher, however, is neither a trained counselor nor a social worker. That knowledge becomes power. A really charismatic teacher can end up running a ‘school within a school’.
In the classroom, the teacher will often employ techniques (and texts) which take students to the extremes of emotion or logic, and will then triumphantly show them how they are holding they key to resolution (‘At this moment, you have agreed that life has no meaning -- but here is the answer’).