There are some possible explanations for the above scenario:
1) The driver is simply an inconsiderate parking idiot; or
2) The driver may have parked in that manner because the car on the other side may have parked out of boundary. (Unless its a 2 lot cluster), in which case that driver is the inconsiderate parking idiot.
Considering its the last lot, here's essentially the probably outcomes:
1) You can squeeze and park tightly next to him (which you did) and possibly hinder the opening of the passenger/driver door (depending on reverse or head-in parking). However, the downside is, if the driver/passenger are inconsiderate idiots to begin with, as per scenario (1) above, you have to be prepared to live with the fact that your car will possibly be dinged and scratched because they won't give a hoot and force their way in if they can.
2) If the driver of the car parked on the centre line was not the parking idiot as per scenario (2) above, your action would most likely cause him the same reaction as you had and that may translate to him possibly dinging your ride as well as cursing you for being a parking idiot as well.
2) Knowing that the space can be very tight and if you value your car and its aesthetic appearance, you can either wait for another alternative lot to come by, or park with the other side of your vehicle very tightly to the other side, closer to pillar/lot cluster divider (if there is one). Win-Win, you are the bigger person and the other driver would probably have no consequence to your life or frustration.