I dont think they are.They are as important to see that justice is done as the Prosecutors. I think where the dislike comes in is because most defendants are quilty and convicted. Without defense attorneys there would never be a resolution one way or the other.
And of course it depends on the behavior of the defense attorneys in court. Frankly Baez and Steve Feldman in the Westerfield case were slime imo.
Some of the best attorneys I have ever seen have been defense attorneys.
Who are respectful to the witnesses, to the court, and knows the case inside and out and are great examiners. I am very glad that innocent people have found such attorneys to fight for them.