The Magpies slumped to a 4-0 defeat against Tottenham Hotspur on Wednesday, and questions have been raised as to the desire of those selected by Alan Pardew.
Pardew admitted after a midweek home humbling that his side had not given 'life and limb' for the collective cause.
Williamson acknowledges that criticism is to be expected after three straight Premier League defeats, in which they have conceded 10 goals and scored none, but the centre-half rejects any suggestion that the Newcastle squad do not care about performances and results.
He said in The Northern Echo: "It might have come across to the fans that there was no heart, and that's a disappointing thing.
"Sometimes, the fans can be a little bit unfair, but you can't say that over the past few games. They are justified, and we completely understand their anger and upset.
"Believe me, the players in there are feeling exactly the same. Now, it is all about getting that reaction and making sure we can convey our spirit and fight against Villa, when we've got to bounce back.
"What we have had at this club in years gone by is a reaction, and so when things like this do happen, the lads pull together on the training ground and go back to the basics of working hard and making sure we are compact and solid. Hopefully, that's where we are going to go."
Clearly angered by the display of his side against Spurs, Pardew tore into his players during a post-match dressing room rant - and Williamson admits he was well within his rights to do so.
He added: "We've seen that side to him before. Every now and again, when it is necessary, he tears into us, but there needed to be some harsh words said because he felt it wasn't good enough from the players on the pitch.
"First, you do it for yourself, then the manager and the fans and the club. That's where it builds from but, yeah, we have let the manager down.
"We have let the fans down and we have let ourselves down, so it is all about getting back to the basics now."