Dan, please do not hate yourself for being trans. Don’t let this wrong headed argument make you feel bad about yourself or make you want to harm yourself. I think it would be a good idea for you to talk with someone about your feelings. If you are in Canada or the US you can call this support line for trans people. https://www.translifeline.org
Anyone who ever makes the argument that you are not really a man, can only do so if they ignore glaring facts. Your brain is male, and transgender is simply a normal variant of development that has always existed. As a male you deserve to not be singled out just because you developed differently.
I don’t know what else to say to you, except that these people are wrong and there are a lot of people that disagree with them. It’s pretty obvious to me when I’m interacting with a man or a woman. I’ve yet to meet a trans person whose gender identity didn’t seem perfectly natural. My point is, you are a young person, so it may be hard to see now, but there is a wide world out there with all kinds of people who will see your humanity, and who will understand that you are male, you are a man. It is my sincere hope that you believe this yourself, and that you love yourself.
I’m a cisgender woman, and I’m in love with my girlfriend, a transgender woman. We have a wonderful life together. You can have a wonderful life too, there is a lot to live for and a lot to look forward to.