About the Slytherins/Dumbledore conflict

I think Dumbledore showed some bias against the Slytherin House at least in the first two books.

Lets look a bit at this scene from CoS:

Dumbledore says that Harry had many of the qualities that Salazar himself wanted in his students and he then mentions:"Yet the Sorting Hat placed you in Gryffindor. You know why that was. Think."

To which Harry responded, "It only put me in Gryffindor," said Harry in a defeated voice, "because I asked not to go in Slytherin . . . ."

"Exactly," said Dumbledore, beaming once more. "Which makes you very different from Tom Riddle. It is our choices, Harry, that show what we truly are, far more than our abilities."

Dumbledore makes it sound like Slytherin is the bad choice (which makes you wonder why he sent Hagrid of all people, someone who dislikes Slytherins, to get Harry and whether it was intentional, but maybe I'm just paranoid). Now I personally see 3 explanation about why Dumbledore is so eager to paint Slytherin negatively to 12 year old Harry, who is likely to take his words at heart and see the Slytherin students as potentially evil:

1)Dumbledore is right and Slytherin is a bad choice. Despite being a Slytherin myself, I can understand the sentiment. Slytherin has produced the most dark wizards and while not all Slytherins are evil they at least mostly seem like jerks in the books.

2)Dumbledore is wrong and biased and perhaps that's why Slytherins seem to dislike him and want him replaced. After all he did rather cruelly give them hope they would win the House Cup just a year before, just to give it to Gryffindor at the last moment.

3)Rowling intended Slytherin to be the evil House at the beginning of the series, but then realized it didn't make since to have a House just for the evil kids so she tried it to redeem it with later interviews about how Merlin was SLytherin etc.

Also, keep in mind that when talking to Snape in the memory we see in DH, he said something along the lines of "I think we sort too soon" like he wanted to free him from the Slytherin curse or something.

If you think I misunderstood these scenes, you're free to explain what you think Dumbledore meant there. This is not a Dumbledore bashing thread, this is just for analyzing the series something I love doing nowadays that I have so much free time.