In my example I wasn't trying for literal exactness. Assume with my own kids I'd tell them what I thought long before hand. What I wouldn't tell them is that "I knew" things I didn't know.
As for absolutes...
Don't take another's life. Don't steal from someone. Don't lie to defraud someone of their value or property or self worth.
You can add as many as you like as a lot of things fall in this sort of category.
The bottom line is though these things are just idealisms if there isn't some absolute value in them.
If I truly lived an existence where truth was relative and only internally conceived and perceived, I'd do whatever I pleased and sleep soundly at night. Why not steal? Why not murder? Why not lie? If you have something and I want it and can get it for free without being caught, why not take it?
If I am caught in the act and will lose my job and family and go to jail for it, why not kill the witness if I know I can get away with it?
We are biologically wired to conform to some extent to the traits that keep us from doing this but people override that all the time. We aren't puppets or robots who must obey the program...jails are full of people who don't.
So why accept these things when they interfere with achieving our goals or satisfying our desires?
In the case of unrestrained and unrepentant murder and thievery, you will find few people aside from genuine sociopaths who will routinely do those things and be able to conscience free say they are untroubled by them.
We have these laws apparently strongly imprinted on us--yet not so strongly that we can't break them simply as an act of will. Why then do we value them as truth?
If the programming isn't making us do it, then what is?
At the age of six, I was minutes away from stabbing someone to death--coldly and without emotion--simply as a practical matter no different than going to the bathroom. I can clearly recall it and know exactly the state of mind I was in at the time. I had no fear, no conscience about it and then something visceral literally stopped me in my tracks--against my will. It angered me but I could not resist it despite my intent to do so.
If you have enough experiences in life like this you come to realize that we are more than the sum of our parts and there is more than just "what we think and decide" or "biology".
If you haven't had these experiences, then you can make up any sort of "truisms" you like and call them all "valid". If you don't value anything as absolute truth within yourself then you have no absolute value within yourself for others.