I don't know if we can even argue that it's disproportionate. Anywhere you go on the web, this is all anyone is talking about. It's not media companies shoving the story down our throats - this is all the working class wants to be talking about right now. With this much public attention the response is going to be proportional to the amount of people who are paying attention to this topic.
I get that this person isn't as important to care about compared to many many other people suffering and being killed around the world, but we can't deny that a huge huge number of people are interested in engaging with this topic and some of them even want the shooter to be found.
24 hour analogue clocks exist. I have a 24 hour watch which only revolves once per 24 hours. It's a disadvantage though.
The reason why clocks and watches display 12 hours at a time is so that they have space to show finer resolution of time. If you try to cram 24 hours onto a clock, it's not easy to tell if it's 12:20 or 12:30 at a quick glance.
Most people are not too stupid to be aware of if they are in the first 12 hours or second 12 hours of a day, so they benefit from a watch with 12 hour timescale and finer resolution so that they can more easily see exactly what time it is.
And for all the dummies posting about 12h vs 24h clocks. In the sense of saying that it's 1pm vs 13:00. That's not what this meme is even describing. This is about the physical layout of a clock or watch face.