Berger's book is an ugly hit piece written by a bitter, angry and jealous man. Sue Fishkoff's "The Rebbe's Army" is a much more objective and balanced book.
There are pockets of silly messianists in Crown Heights and Israel, but the shluchim and the movement's leadership have moved on.
In the LA Times article you will find a quote from Rabbi Yehuda Krinsky which exactly describes Alouette's opinion of the "messianists." BTW my son is married to Rabbi Krinsky's granddaughter.
He seemed pretty exercised, particularly about the fact that other Orthodox didn't take his concerns all that seriously. I read it with a healthy grain of salt.
There are pockets of silly messianists in Crown Heights and Israel, but the shluchim and the movement's leadership have moved on.
That seems a reasonable approach if the messianist "movement" is indeed waning rather than waxing. This is the kind of thing where you aren't likely to change people's minds. Better to let the passage of time take care of the problem.