My flight this morning had to return to the gate after a passenger had a heart attack. We had pulled away from the gate and were waiting to take off when the FAs came on to announce we would be "returning to the gate to off load a passenger who had just had a medical emergency." Immediately people started complaining (LOUDLY) about missing their connections. This continued as we pulled back to the gate, as the EMTs came on the plane to get the passenger, and even after we were airborne. The complaining resumed once we landed (at the one of the airline's largest hubs) and even after the FA stated that it had been a heart attack. I can understand being worried about making your next flight, but the intensity of complaining was beyond what I normally hear for weather/equipment delays. Did they suspect he caused his own heart attack? I am still in awe at the lack of human compassion I experienced this morning. The guy behind me (worried about missing his connection to Maine) said after landing "we've been to hell and back on this flight, how dare they not offer to hold our next flight!" We were 40 mins late landing. I just checked the PHL-PWM schedule for today, 20 flights, 6 direct. I have a feeling they ended up getting there. These complaints and comments have been bothering me all day, I just can't believe the lack of compasion. Is this becoming the standard? I'm hoping I just had a bad group around me.