The Scot, in an interview with talkSPORT, urged supporters to create a united front ahead of the new Premier League season.
Despite the signings of Joelinton, Allan Saint-Maximin and Jetro Williams, the Newcastle faithful were livid with the hiring of new boss Steve Bruce. Fan groups are attempting to organise a boycott of the Magpies' top-flight opener with Arsenal.
But Ritchie says: "I don't understand the unrest - I've got to be honest.
"The club's gone out, spent money. We're pushing, trying to compete with the teams we can compete with and you have to be real.
"To compete at the top of the Premier League now is mega, mega money - I think the owner has been honest in his interviews in the press and said he can't go and compete with them.
"He's been upfront about that, and to do that he would have to sell the club.
"For me we have to all be in this together.
"I've said this since I arrived at the football club - there's always been a little bit of unrest - but the main thing I took from Bournemouth, and it's a smaller club I know but everyone was pulling in the same direction with the same philosophy, mentality and desire to help one another.
"That's what we need to be here - the fans, the staff and the playing staff - all as one - and pulling in the same direction.
"That's something I'm really passionate about - if we're all in this together, we can be a lot stronger and we need the fans to support the team, and be with us."