I don't think any were really saying it was inferior, I prefer not to get into discussions about performance, unless there was a big difference then other factors were more important. The Hurricane was inferior in almost all respects to the 109 but did its job perfectly adequately in 1940 despite being approx 30 MPH slower.
The P51 didn't have to be superior, it just had to be there, even an Me262 could not press home an accurate attack in the presence of an escort. The P51 couldn't catch it except when landing but the 262 couldnt slow down while attacking bombers either. Similarly with LW prop fighters the extra armour carried to protect from bombers return fire hampered them in combat with escorts. From what I have read if an escort and a defender get locked in combat then neither are doing their job. The escorts job is to stay with the bombers and prevent attacks not get involved in 1 on 1 combat. Similarly the defenders job is to attack the bombers or "escort" those attacking the bombers.
Later tactics by the USA where the P51s and others actually hunted down the LW in front of the bomber stream and at their bases were unusual and reflected the massive numerical superiority that the allies had. The LW would have liked to do the same in the BoB but they simply didn't have the numbers to do it.
Soren has stated several times in this thread that 109 was superior to the 51...