How can I be respectful as a tourist?

Hello,

I am taking a cruise with some friends out of Barcelona soon. My grandmother immigrated from Spain, and I have always wanted to see it.

-I am not willing to cancel the entire trip. I'm not staying in Barcelona, and don't really understand how I'm contributing to any problems with rent prices. But I want to be respectful. Are there areas I shouldn't go to? Other things I can do to be respectful?

-Is the anti-tourism sentiment from a loud minority, but most people want the tourism dollars Edit- euros to help the economy, or do most people feel this way?

Second edit: Some people are commenting on the cruise exhaust. This is very surprising to me, since I have a view of a cruise terminal from my home and it does not change my air quality at all. I apologize for that, I can't imagine why it lingers there but not here, but I never would have expected it.

Thank you.