Southwest Airlines has replied to me. They did not attempt to explain nor justify the blocking of these services, and they refunded my $8 in full.
Here is their note in full:
We're sorry to learn that your recent inflight WiFi session was less than stellar. We assure you this was not representative of the high quality product we are proud to offer and apologize for any inconvenience this may have caused. Since you were not able to take full advantage of the WiFi connection, we have refunded the $8.00 you paid for this service to the VISA ending in 8636.
We hope you will try our inflight WiFi again the next time you are onboard one of our WiFi-enabled aircraft.
-Your friends at Southwest Airlines