There is a lot of stupidity on this thread.
I've been flying for over 35 years, I have over 25,000 hours. In the last 22 years I've spent 16 years as an Airbus captain with over 600 different F/Os to fly with. There is no issue flying with someone you don't know. We are all trained and checked to the same standards. We fly under the same procedures, SOPs, and we are checked to see that we stay standardized.
Inevitably there will be someone you don't care for that you are paired with. It doesn't matter, you just fly the trip and go on with your life. No one at this level of flying will be allowed to go beyond the limit that their personal beliefs or quirks will affect safety. If there is such a breach of protocol either pilot can call the chief pilots office and get themselves or the other crew member removed. The union professional standards committee will also be involved.
In the USA we don't have cadets flying large transport catagory aircraft. You spend some years working your way up the aviation ladder. If you have a questionable reputation you will not make it to a major airline. Even in the US aviation is still a small world. Your bad reputation will make itself known. I am not saying that this F/O would have been caught out earlier butI think this is where the cadet system breaks down. Issues in the US are usually caught long before they rise to the major airline level.