I think that with a few more hours under your belt and a bit more confidence you might challenge an instruction like that next time.
It is never good practice to join and make a ninety degree turn thus reducing visibility and options in a high work load area.
As others have suggested, a left base or over head re-join would have been a safer and more practical option. Alternatively, you may have considered extending out to to the West well beyond the circuit before making your ninety degree turn.
Personally, I would say that irrespective of any ATC instruction, you are the Commander of the aircraft and you should challenge any instruction which you may feel compromises the safety of your flight. If the instruction stands then it is down to you to apply your own safety margins (ie join from a more Westerley position). Any unusual manoevre which reduces your ability to see in the circuit is best avoided.
You probably learned a good lesson and probably won't forget it.