Kills lasers? No.. that isn't really possible... at least not for a noticable degree. Remember that all the laser is is a light source. It doesn't read anything, rather the optical sensor does. You could stick a piece of cardboard in there and it wouldn't effect the lasers life span.... it'll be on during the whole read regardless and the optical sensro is incapable for getting more laser light than what it gets from a pressed disc, seeing as how rewriteable media is duller.
Actually, it is possible. Lasers have a lifespan, just like a lightbulb, LED, or any electronic item which generates light. If the laser is having a hard time reading a disc, that laser is on longer. If it takes twice as long, due to re-attempts to read the data, the lifespan is halved. When the power output pot is tweaked to read media for which the unit was not designed, this also accelerates the demise of the laser, as it is usually tweaked for higher output.
Now as for the drive assembly, I suppose it's theoretically possible. The tracking motor, unlike the laser and sensor, has moving parts. When a dvd player can't read media it makes several attempts before giving up, so if you put media with errors in it in a drive I suppose the motor would get used more often. I don't really think that it would be a significant amount though, unless you are constantly putting in bad discs and trying to play them. Also keep in mind that any extra wear and tear balances out. While the startup sequence might take more passes for a RW disc, once it gets started, the disc spindle will spin at a much lower rate because writeable media has a slower read speed than pressed discs. So you are trading off stress on one motor for stress on another.
Again, the longer it spins while trying to read data, the more wear and tear on all of the components. The focusing mechanism, the head motor, the cheap plastic rails, ....everything. Also, when the device has difficulty reading a disc, it will try altering spin speed, up and down. The PSX would notoriously go into a high speed spin and lock up with some media. This is something it would not normally do, so wear would be increased.
I have an earlier Pioneer DVD-R set-top recorder which hates just about any media other than Verbatim. A fresh drive will work for a while with anything, but dies pretty quickly with the cheap stuff. I replaced the mech twice before deciding to only feed it Verbatim media. It's been fine ever since.
I voted "1", not because I'm a "sheep", but because I know better from much experience with such issues 
I think you missed the part about "not to a noticable degree".

I've had some dvd drives for 5, 10 even 15 years and they work just as good now as they did when I bought them. A few of them almost exclusively had re-writeable media in them. My point was exactly your point actually.... a laser is a lightbulb, so it doesn't matter if the room is painted balck or white, it is still on the same amount of time and will burn out at the same time.
Also I think you are assuming that a re-writeable drive has trouble finding the data. As far as I know this just isn't true. The initial seek time might be longer (because it's looking for a specific read speed and isn't finding it) but once all the ducks are in a row it'll read just as well as any other disc.
Yeah, longer read times will wear on the components, but not as much as higher rpms will.... things that spin tend to shake things apart.
I get what you are saying with the old drive you have, and I've ran into that issue myself, but the flaw in your logic is that you are equating one problem with another. The drive is going to wear down over time regardless and pressed discs just have a clearer image. Your drive isn't having trouble reading a burned disc because burned discs are wearing it down, but rather it's wore down on it's own and thus the burned discs are harder to read. Either that of it's just a crappy model drive.... that happens too.
It's like a guy that regularly eats steak saying that steak made him weaker because he could lift 75 lbs when he was 30 and only 45 lbs when he was fifty. The think the fact that he's 20 years older might have something to do with it.
The kind of wear and tear you are talking about (trouble reading the disc, longer read times, ect) would come from a disc that the machine can't read well and/or is damaged. Well what do you do to a disc like that? That's right, you throw it out! And since we all know one or two bad reads isn't going to make a significant difference, the only way to wear a drive down would be consistently and regularly feed it unreadable or barely readable discs for it's entire lifespan. Absolutely nobody does that.
Finally just put it into context. This was a Wii we are talking about there. So at the most it's 5 years old. It was around a year before they got rw media working on them and even then it was anther 6 months to a year before softmodding came into play. So the guy was saying that using burned media on a drive that's accepted burned media at the most 4 years was killed by using burned media. Nah that's a bit of a stretch.
I"mnot disagreeing with any of the pionts you made, I just don't see how one thing relates to the other.