The incident has opened a wider debate about the issue of racism in Spain, but Guardiola, who spent time as a player and manager in La Liga, said he does not expect things to change quickly.
"Of course racism is a problem everywhere, not just in one specific place," Guardiola said.
"Everywhere we have [people] thinking we are better than our neighbours, we are better than the other one.
"The problem is that there is racism everywhere. Not just for gender but for colour, for attitudes. We believe that our language is better than the other one, our country is better than the other one.
"We need to accept diversity as a strength, like a human being, and still right now, we are far away from that. Hopefully it can be one step to getting better in Spain, but I'm not optimistic. I know a little bit the country and I'm not really optimistic.
"There are a lot of Black people stepping forward to defend what they should not [have to] defend. Hopefully justice can help to do it, but at the same time, is it going to change anything in Spain?"
Guardiola said he wants to keep his team in rhythm when they play at the Gtech Community Stadium on Sunday, adding he is expecting players to soon start knocking on his door to ask if they are playing against United and Inter.
"They will come, but not yet," Guardiola said.
"I have a vague idea [of the teams for the FA Cup and Champions League finals]. United play completely different to Inter Milan and Inter Milan are different to United. We have to defend and attack differently. Can players adjust better? First Brentford, see what we have to do."