The Guardian isn't perfect, but you can't seriously compare it to Breitbart, which intentionally distorts facts on a regular basis, and goes out of it's way to sensationalize and offend.
Would the guardian be caught dead printing these? https://www.mediamatters.org/blog/2016/08/17/breitbart-news-...
Or have they peddled lies as big as these ones? https://www.snopes.com/climatology-fraud-global-warming/ https://www.snopes.com/immigrants-california-wildfires/ https://www.snopes.com/planned-parenthood-satanists/
Look, maybe the media has a left bias. And it's plausible that right-leaning sources face more skepticism. That's not fair. But the reason Breitbart gets flack is because they really are that terrible.