All the things

Why do you say no?
Did you know that using an image without permission is against the imgflip's Terms & Conditions?

This isn't a copy written image. If you believe it to be, then contact the imgflip people and talk to them about it. This image is everywhere and the users on this site aren't making money from it so it isn't illegal. You're just complaining to the wrong people.

"This isn't a copy written image." What do you base that statement on? If you look at
http://hyperboleandahalf.blogspot.com/2010/06/this-is-why-ill-never-be-adult.html, you will see the image used above is the 4th image on Allie Brosh's blog post. If you then continue scrolling down, you will see a copyright paragraph in the right-hand column; alternatively, if you go to the end and scroll up a bit, you will also see a copyright notice there.
If you check out the Creative Commons license she used, you will see that it requires anyone using her images to give her credit. Therefore, using the image without giving credit is illegal, and also against the terms of imgflip.

I have in fact been flagging as many images as I have time and energy for, asking imgflip to remove them for violation of terms of service.

I know that the image is everywhere. I know that many people do not know the image is copyright -- that's why I try to educate. Sometimes, my messages are not worded as well as others, but I do my best.
If pirated copies of a small-time band's latest CD were everywhere, it would still be illegal and wrong to make more copies. Same goes here. Once someone knows it is a copyrighted image, the right thing for them to do is to delete the image or follow the terms of the copyright.

I worry that the proliferation of credit-less copying will reduce the income stream for small-time artists & creators such that they no longer have time nor energy to create content.

Like I said, you have a problem with imgflip using this image or others using this image, talk to the owners of this site and other sites. I've used the "x all the y" image several times and I'm not deleting any of them. I'm not making money off of them, so good luck with that.

I am doing my best to talk to the owners of imgflip. Just because they have not removed the image yet does not make it right for you to use it.
If you were playing a recording of a local band for parties, and got asked to stop because it was a pirated recording that the band made no money off of, would you stop? The right thing to do would be to stop or to buy the legal recording. Do you disagree?

Please do not make memes with someone else's copyrighted artwork!

If you share someone else's artwork, please give them credit!
Thank you for being honest and allowing artists to make a living.

If you are the owner, contact imgflip and request removal of the templates and the memes that do not give credit. Otherwise, get off your sanctimonious podium cause no one is listening to you.

I am not the owner, but I have indeed requested removal of the templates and memes that do not give credit.
I am sorry you see me as sanctimonious. I worry that the proliferation of credit-less copying will reduce the income stream for small-time artists & creators such that they no longer have time nor energy to create content.

I believe only the owner can do so...

You may be correct that imgflip will only listen to the copyright holder. That would be too bad, since that then means the copyright holder bears the burden of the time and energy required to try to remove illegal copies. It seems like it should be sufficient for someone else to show that the copies are in fact illegal.

ill stop using it (but im not gonna delete the one which i already made)

Thank you for being willing to stop using it.
I would be grateful if you were also willing to delete it or add Brosh's website (hyperboleandahalf.blogspot.com) to the image. Otherwise others may continue to use your image without Brosh getting any credit.