xThough looking at someones travel documents may be unnecessary, it is hardly complaint worthy.
Yes, it is most definitely worthy of a complaint as if it's not stopped immediately such practices will inevitably escalate to the point where a screener will feel free to look through any and all of one's documents. We've seen it and heard about it many, many times.
Was it here or on the blog that I read about a screener who looked through all the papers that a young student was carrying with him, i.e., his homework assignments!