It is a difficult subject to talk about, but believe me, you are not alone. As a constant victim, I can agree that people do not generally stand up for you or step in to offer solace. 99% are much more comfortable stepping in after everything is said and done and offer their comfort now, usually in the form of rushing me to the ER.
Personally, I agree with your assessment that people do not help and that you are one of the very few that has stood up; to which, your reward is to be victimized as well! I discovered that as well on many occasions, but my observations have turned up something else. Many people do not want you to interfere.
There is a "contest" aspect to bullying, even in the mind of most victims, that require them to combat their situation alone or seemingly alone. I can't quite understand it, but I know I do it myself.
As for the question you introduce in the second paragraph, "How do you stand up against bullies if there is no way to do so," there would be no way to do so in the manner you've posed it, but I would like to offer an alternate question.
"How do you make the bullying stop."
Sadly, and specifically against your post, the best way is to simply ignore it. You get as much success as you put effort towards, and believe me it works. But if you are uncomfortable with that answer, then you will lament the other choice in my opinion. As a life-long researcher of people and their reactions, as well as someone that has been forced to learn how to fight and combat against the world, the only other option for how to stop a bully is to make them stop.
Now, perhaps I should explain myself. By ignoring a bully, I mean that you must make bullying "boring" for your attacker. Bullies are looking for some sort of reaction, and if you give it to them, they are fulfilled. If you do not give them a reaction or make it too dangerous for them, they will stop. One way of making the action of bullying too dangerous or boring is to get some form of administration of your school or work involved so that it becomes a public matter.
In the other way, "fighting" your bully, you have to expend thousands of times more effort because you must understand your opponent. I have been forced to used this method on many occasions due to the natural ability of my usual bullies to ameliorate themselves with the administration I am associated with (school, work, etc.) and this makes the first method difficult. You have to understand your opponent if you wish to do this and I will not teach people how to do that, but once you do understand them, you can make bullying a non-issue. This is done primarily by making their action punishable.
I am not a proponent of physically fighting people. I've stayed away from physical terms and suggesting fighting. What I suggest is a mental game, a "mind-game" if you will. The idea behind this is to not allow bullying to take place by making a single move that does not strike at your opponent's body, but their mind. If you find yourself against a "bully," you will find that 9 times out of 10 they are weak willed and unable to rationalize. These types of minds are easy to manipulate and crush with the right pressure.
If you cannot ignore them, (which I highly suggest) then learn to use your mind against theirs.