Why do Many gay people hit on straight people why Not a Gay person like them do you think thats Wrong?

No it's not wrong to hit on someone you don't know is gay or isn't gay.

it wouldn't be wrong for a girl to hit on a guy only to find out that he's gay and it wouldn't be wrong for you to hit on a girl even though she's not attracted to you

When I walk on down the street and I see a man I may look at him and think,  that is nice.  From that point in time the only way I can progress is to do something,   such as maybe speak to that man.   

This is the exact same process that mankind (men & women) has followed for as long as we have existed.    If no one made the first move,  the species would be extinct.   Now 9 in 10 of these advances go nowhere so you move on until the next comes your way.      The only way you can know if you have a chance is to explore it.   Now if I as a gay man take a liking to another guy and he is straight,  then he is one of my 9. (in 10)    The world wont end for either of us if that happens. 

What is interesting is the number of alleged straight men who are in fact open to a little same sex sex.  

To sum up.

If we could all read minds, then no one would hit on another person who we had no chance with,  unfortunately we cant read other peoples minds and so the only way to know is to make a move and see where that goes.  

I doubt you have any basis for making this claim. As a general rule gay men go to gay-only or gay-friendly venues because of discrimination against us and it is safer for us to relax and socialise in such venues. If you see a man in one of those venues he will not be visiby demonstrating his sexuality. Therefore, you may go up to him and start talking and flirting. If he indicates he is not gay that does not mean you must cease any conversation with him but any chatting up would stop.

Gay men are interested in consenting male adults. Therefore, if a man basically says no you do not continue to, as you phrase it, 'hit' on him. Indeed, you would do the same if the other man were gay and indicated he was not interested.

It wouldn't be deliberate.  No-one has 'gay' or 'straight' printed on their foreheads!  They take a chance that you're gay and obviously, sometimes they make a mistake.  It's not 'wrong' - and all you have to do is say, "Sorry, I'm straight."  It's no big deal.

Gay people hit on you because they think you are gay... it's an accident, a gaydar failure.