In a perfect world, I don't think anyone would care about how someone used to be. It should be obvious, after all is said and done, that it's how a person actually is that's more important.
A guy could have been, for example, a real asshole in high school but be a great friend now.
And even more important than how a person is would be how a person will be.
Like, a girl could be a total slut now but eventually she could settle down and be faithful.
There are three problems with all of this.
1. It's not a perfect world.
2. We can't see into the future, so we have to make guesstimations based on present and past behavior.
3. Sometimes past and/or present behavior simply cannot be ignored. See numbers 1 and 2 above.
To summarize, I don't know what the fuck I'm doing.