You 'know' they are a good and legal company in China? Are you currently employed by them? Are you using an alias?
Just because they are treating you well now doesn't negate the fact that numerous teachers have been- and are still being cheated, mistreated and threatened by them.
Please state more clearly what your experience is.
ps. looking at your English I think Tianshuo is right up your alley as they don't look too closely to what kind of teacher they hire.