Yes. Some yaoi is good and some is not so good. I tend to seek out the more serious and beautiful yaoi manga (although comedy can be good too). I think the entire genre has been perceived badly by some because yaoi is mixed, all of the stories vary in quality that appeal to different people. Unfortunately, someone many get a small glimpse of the less appealing yaoi that will therefore cause them to forever view yaoi as trash. Overall, I like yaoi very much, just not all of the stories.
Yeah. Oftentimes, yaoi ends up crossing over to completely non-yaoi series and that can trip people up, unfortunately. Well, everyone likes their own stuff how they want it, I suppose.