The problem is that Paste plugin automatically resets plain text paste on every paste. So all we need to do - set it back. The following code should help.
tinyMCE.init({
...
oninit : "setPlainText",
plugins : "paste"
....
});
The definition of setPlainText
function setPlainText() {
var ed = tinyMCE.get('elm1');
ed.pasteAsPlainText = true;
//adding handlers crossbrowser
if (tinymce.isOpera || /Firefox\/2/.test(navigator.userAgent)) {
ed.onKeyDown.add(function (ed, e) {
if (((tinymce.isMac ? e.metaKey : e.ctrlKey) && e.keyCode == 86) || (e.shiftKey && e.keyCode == 45))
ed.pasteAsPlainText = true;
});
} else {
ed.onPaste.addToTop(function (ed, e) {
ed.pasteAsPlainText = true;
});
}
}
So now it always will be plain.