::Sigh:: I hate it when I show up late to these topics. ::Rolls up sleeves:: Here goes.
Racism, like any other kind of ism, is not about hate. It's about laziness.
See, it goes like this: people's lives are complicated. Deciding whether or not to have coffee with breakfast in the morning is easy: do you feel awake enough? If not, have some caffeine. No, I'm talking about the difficult stuff: do I invest this $3,000 windfall I've got right now, or do I use to fix the problem I've been saving up to fix for the last four weeks?
What does this have to do with 'race?' Well, it has more to do with your brain. People like to make their decision making easier by lumping things into groups. "These are anise-flavored jellybeans, I don't like them, ergo I will not buy this bag of jellybeans." We make hundreds of sorting decisions like that a week, sometimes a day if you've got a lot of decisions to make. Facing down that many decisions is daunting, because you want to get things 'right,' but that's a lot of data to process. So you sort things.
The problem is that this process is used with everything we have to do. We always look for patterns and sort by them. We even sort people this way.
About 65% of the time it's harmless. You can make assumptions like 'He's from Georgia; he's eaten peach pie before.' The remaining 35% of the time is where we get into trouble. It's also super easy to do so, because our principle sense we use for sorting things is sight. The 'races' as they are traditionally defined, are based on physical characteristics that can be observed, which is a horrible distortion of the truth. People even from very visually different 'races' are typically quite similar genetically, since all the things that make humans come in different sizes and colors occupies about .000000001% of our total DNA. The rest is basic life-functioning (how to form cell walls, how to process proteins, that kind of thing).
But it's hard to treat people like individual snowflakes. It's much easier to treat them as groups of people. Helps in the sorting and the pattern recognition. The problem is that 35% can give you a very skewed lazy view of the world, which will disadvantage you and those around you quite a bit. Most cultures on this planet are fine with you digging your own grave, it's when you drag other people in that it's a problem.
Worse yet, this problem compounds itself. If you segregate a 'race,' then they will tend towards the same culture, because you're forcing them too. People with extremely racist perspectives take this as prima facie evidence that they're right. Look up self-fulfilling prophecy. That sort of thing.
Even more worse yet, because this is natural human behavior and it exists only in the human mind, it's incredibly hard to police it, and sometimes even to identify it.
Racism isn't about hate. It's about using hate because you don't have a different option, because you haven't trained yourself out of not just lumping a group of people together in a simple group, like 'money-loving Jews' or 'violent Italians.'
