:bism: (In the Name of God, the Most Beneficent, the Most Merciful)
(Peace be upon you)
...how can I prove to my dad that I'm not?
I'm sorry to hear that your father is becoming troubled with you using this site; however, I'd note that you should still obey your father as brother Scimitar wisely recommended. When I started practicing Islam, what didn't I hear from my parents. They'd make fun of my
salat (prayer), constantly dissuade me from fasting during Shahru Ramadan in case I became too weak to study, and my mom had point-blank told me that she'd refuse to talk to me ever if I decided to wear the
hijab. They'd even ask me if I was planning on being a terrorist and wondered out loud constantly if I was planning on becoming an extremist. It was difficult in the beginning to show them that I'm just the same person they love but that something inside me had changed, but I knew I couldn't do that with words alone; so, instead of responding by being difficult with them in return, I'd instead just make
duas (supplications) for my parents and decided to become my best with them. Both my parents came around to accepting of the change in me.
Brother, what we don't need are more people to tell others what Islam is or isn't but we should as much as we can try to embody what Islam is within our character; of course, we'll have flaws and foibles going forward no matter our efforts as simply part and parcel of being human beings, but we should as much as possible still try to succeed and try to introspect wherein we're going wrong with others and try to correct ourselves wherein possible.
Remember Prophet Muhammad :saws: said, "I was been sent to perfect noble character." Be patient with your parents, especially your father, because you owe him that respect. This respect doesn't meant that your father is allowed to oppress you in any manner as I should note, but this respect does mean that you listen and obey your father in recognition of the fact that he's concerned for you and wants the best for you and this honor is his right in Islam.
While I'm happy that you're on this site as a wonderful little brother, I recognize that you should be concerned about making your father happy with you as that's wherein Allah's happiness lies. Please do not make the mistake of arguing with your father as then he'd turn more intractable as arguments are poison in situations like that; instead, show in yourself the willingness to humble yourself before him. When he's cooled down, invite him either to browse the site himself at his leisure or to join this site himself so that all of us Muslims and non-Muslims alike can perhaps benefit from his wisdom and experience. And as always, be patient with anything of concern, because Allah has said in the Quran that Allah is with the patient (2:153). Patience will win you that which arguments never can - the heart.
:wa: (And peace be upon you)