Songwriters often feel very strongly about things and urgently feel like they need to share their message with the world. This sort of impulse goes with the territory of being an artist, I suppose, although some feel the need more acutely than others. Young songwriters in particular often feel the need to try and make people change their ways, or see the world from their point of view.
However, I want to caution you to tread lightly when trying to "convert" the world to seeing things your way. This is not to say that you shouldn't feel passionately about things or even that you should compromise your view. If you feel strongly about a subject, you should definitely express your feelings about it.
This is more about being effective in your modes of expression; what good is shouting at people and telling them "what they should do" if you're only going to turn them off and make them even more determined to ignore your pleas? No one wants to be lectured to or told what they're doing wrong. To do so comes off as the height of arrogance and serves mainly to alienate the listener.
At best, songs that chastise the listener in the second person serve mainly to galvanize fans who are already converted to the singer's viewpoint and agenda (i.e. the proverbial "preaching to the choir"). While these songs DO have a place within certain genres (punk, heavy metal), and can help "rally the troops," they primarily serve a cathartic function and the writer shouldn't expect much in the way of actually changing anyone's behavior. (You probably shouldn't expect much change, either way, actually.)
My personal view is that it's much better to seduce the listener, or give them food for thought, rather than try and jam an opinion down their throat. Any moral debate actually worth having is loaded with nuance and grey areas - no one really needs a song telling us how immoral it is to shoot someone for kicks - and the mature songwriter recognizes this fact. As a result, he tries to shed more light on his own viewpoint or, best-case scenario, he gets people to question something they may have taken for granted in the past. (Leave aside the fact that most people only want entertainment and don't listen to popular music for enlightenment or politics and would consider it foolish to do so.)
To illustrate my point, let's look at two songs on the unlikely song subject of vegetarianism. First, consider the well-known title track from The Smiths' 1985 album, "Meat is Murder." If you've never heard it, check it out here:
While The Smiths recorded some great songs and remain a critic and fan favorite to this day, you really have to wonder who THIS song is appealing to exactly, and whether or not I agree with the message of the song is beside the point. While the goal might be to "unsettle" the meat-eating listener with the sounds of animals being led to slaughter (and there's no doubting Morrissey's sincerity and passion), I can't really imagine anyone listening to this and changing their carnivorous ways. Good intentions aside, it just comes off as too petulant, overwrought, and condemnatory to be effective. As a result, the song serves only as a self-congratulatory anthem for the already-converted, and I doubt even THEY enjoy listening to the repeated moans of a doomed bovine.
Now, contrast "Meat is Murder" with this song from 1982, "Torture Me" performed by punk legends The Damned and written by band member and avid animal rights activist Captain Sensible:
"Torture Me" is about the exact same topic as "Meat is Murder." but is arguably far more effective, despite its lesser-known status. Why is this? Firstly, the equally-earnest Captain Sensible, rather than playing the righteous accuser (even if that's the hidden intention) adopts the first-person role of an animal being slaughtered for food. As a result, he immediately casts himself as victim as opposed to moral judge. This is a clever move, and also one that forces the listener (if he's paying attention at all) into an unfamiliar perspective.
Secondly, the band offsets some of the gruesomeness of the imagery by couching the lyrics in a pretty but sad and plaintive piano melody. Rather than putting the listener on the defensive, this strategy makes the listener even MORE receptive to the subject matter at hand. However, despite the alluring effect, the music remains consistent with the tragic theme of the lyrics.
"Torture Me" is a thought-provoking and imaginative approach to a moral issue that's difficult to broach in the context of popular song. And, while Captain Sensible's moral message may be exactly the same as Morrissey's, his M.O. is completely different. Admittedly, like "Meat is Murder," "Torture Me" has probably never won any converts. However, which song do you think is more LIKELY to give the neutral listener pause? Which song do you think the neutral listener would rather hear if he's already decided on the moral issues? Which one feels more like "preaching to the choir"?
As I said earlier, I have no doubt that Morrissey is quite sincere in his unwavering support of animal rights. Perhaps he would argue that venting his moral outrage on behalf of his fans was the whole point of "Meat is Murder." Fair enough. However, if an artist isn't going to appeal to anyone outside his faithful flock, then he's verging on the artistically insular.
Besides, where is it written that the goal of a songwriter is to "make people think like me"? That's an arrogant goal and possibly the height of folly. Don't fall into the trap of trying to overreach the limitations of a pop song just because of your moral certitude or blinding ambition to bring enlightenment to the masses. Recognize the strengths and weaknesses of your genre and make them work for you.
If you want to make people think, don't tell them what to think or how to think. Try showing them things from a different perspective and let them think for themselves. If your point of view is worthwhile, you'll gain far more converts and fans by stimulating their minds than you will by admonishing their actions.
Give people food for thought, but don't jam it down their throats. Even if it's meatless food for thought.