You cannot choose to "get into" a band/artist prior to hearing them...If someone says this, it means that they have probably heard from music critics or music geeks or someone they admire or wherever that the music is "good". However, what music is "good" is entirely subjective based on one's own opinions.
Why isn't it a good idea to try listening to something that has been recommended to you by a source you are favorably inclined towards? It may still end up being something you like. Yes, it's probably not good for you if you just force yourself to listen to things because you think it will make you cool, but it's reasonable to try something from, say, a person who you've already found to have tastes overlapping with yours.
Also, there's the fact that it's nice to share experiences. Thus, I think it makes sense to 'try' to like something that your friends like.
Anyways, I'm not sure if others will agree, but for me personally, sometimes I like to listen to music solely because
I know there is someone I like/respect who listens to it; in other words, the reason why I like it is the associative value. This only comes into play in certain situations, but I thought it was worth pointing out that circumstances can cause you to like music the same way it can cause you to like anything else. For example the music my brother listens to is really dumb and terrible but sometimes I actually want to hear it now that he lives in another city.
Finally, I think when people in this thread have been saying they "mean to get into" a group/artist, they are not implying that liking the music is a foregone conclusion. Sometimes it just doesn't stick, and I imagine people accept that.
I am not sure where to even start with your post. First, I have to wonder if you even like yourself or if you have merely worked hard to construct your likes to appear "sophisticated", "eccentric", or "cool". I wonder where you draw the line between alleged music hobbyists and casual listeners. Are casual listeners people who listen to Top 40 radio or a band that is hugely popular, like the Dave Matthews Band? What makes you so much better than a person who likes music that is popular amongst others? People like what they like; it does not make them bad people. It seems you have a spent a lot of time listening to music; good for you. People who may not listen to these bands likely have other interests, such as athletics, or automobiles, or fashion, etc.; they would likely find YOU and your music obsession uninteresting. It works both ways. Just because someone don't like obscure music does not make them any less interesting, or any more interesting.
I don't think he was putting down casual listeners at all, and I don't think he would disagree with your assertion that they are not bad people, that they likely have other interests, etc. However, that doesn't rule out the legitimacy of his experience or the likelihood that other people may find themselves in the same boat.
I also don't see how you think you are better at listening to music than the "casual listener" because you have to listen to albums and bands you hate at first multiple times before you like them. Repetition breeds content. The more you listen to crap, the more you will like it (not to necessarily say that you listen to crap, but who knows). This is evident with many of the songs on the Top 40 radio station. Many are not good, yet if you hear them every hour, eventually you may find them sticking in your head (at least until the next "new" sound comes around).
He didn't say it was just repetition. Yes, he referred to the process as requiring a period of time, but I think -- and I don't know if this is indeed what he meant, but in any case it's what I believe -- that the key ingredient is intentionality. Repetition will make things stick in your head, but you might not like it. I get Top 40 songs stuck in my head because sometimes that's all I get to listen to when I'm at work, but that hasn't helped me enjoy that kind of music more.
On the other hand, I can imagine listening to these songs in the future if I want to be reminded of this time in my life.
So, your earlier question was probably rhetorical, but I'm going to give my answer anyway:
Are casual listeners people who listen to Top 40 radio or a band that is hugely popular, like the Dave Matthews Band?
Ultimately I don't think it's what
a person listens to, but how
. I had a friend who listens to bands that I see talked about here relatively frequently (my vagueness betrays my ignorance), but she generally just has her music playing on shuffle in the background. I could be wrong, because obviously I don't see what she's doing all the time, but my impression based on how she listens to music when I see her and the way she talks about the music she listens to is that she's a 'casual listener,' someone who just kinda likes the mood it sets when it's playing in the background of whatever she's doing. In other words, she's not really paying attention. And that's fine!