This doesn't sound like a rant as much as it just sounds like a problem you could use help with. Have you tried Nonviolent Communication? It's something I always resort to when dealing with difficult conflicts and it usually takes the heat out of them. I may be able to explain it in more detail if you're interested, but the crash course would be this:
1. Only state facts as facts. If you want to state an opinion, clearly mark it as one.
This may sound easier than it is, because pragmatically, we usually speak our opinions. For instance "You're always late!" is clearly not a fact, since 'always' is an absolute term and there is nobody who is literally always late. "We missed our bus, because you weren't at the bus stop at 9:30" however would be a fact because it can be supported by evidence that can not be refuted.
2. Make a clear distinction between yourself and the person you're talking to. State what you feel at what he or she does. For instance, "I feel like that my time is not taken seriously when you don't show up on time."
3. Formulate what you want into a specific change you want to see in the behavior of the person you're talking to. This of course should be something that person can actually fulfill. For instance, in my example case it could be: "I want you to call me in advance if you're going to be late."