Is downloading content from the internet always ok?

My father thinks that just about everything that can be downloaded from the internet could have viruses and therefore anything and everything that I have ever downloaded from online my dad is threatening to get rid of, despite the fact that they are virus-free and I have checked to make sure that they were not infected. My dad can assume what he wants, but honestly without downloading anything from the internet you can't really do much on my computer. Now, My dad does have a slight advantage in this situation. The computer that I have been using to download stuff on is my school laptop and I have already accidentally messed it up once with terminal commands, but it was a complete accident and it WAS NOT DOWNLOADED FROM THE INTERNET. What really pisses me off is the fact that he is under the impression that the school allows no games on the school computer, yet in spite of this, the head guy at the tech department at my school specifically told me that as long as I don't play them at school, flash and .jar games are ok at home. So, I decided to play a fun game called Minecraft that one of my friends sent me. I asked him before I opened it if he has played it before. He said yes, without mentioning issues or malware. so I began to play it and I have since become an addict. My father threatened to call the school about whether I am even allowed to download things from the internet when I have to do that EVERY DAY ANYWAY to get homework and papers off of the school website. Later my showed me that by going to a website I could use it to edit my in-game inventory in order to make the game easier. So I used that website a few times and I even had Dennis (my friend) do It on his computer first as a virus-check. No viruses, as usual, and then my father saw me do it. He saw that there were no viruses by the fact that I didn't get any- but he still got really mad at me and now he is going to severely punish me; I am assuming he is going to attempt to remove the game from my computer.

Now here is my question. Is there a way to prove to my dad that most everything that can be taken off the internet is NOT always virus infected and is there a video or some good website I can let him see?

Any and all help will he appreciated. Please do not hesitate to give me ideas. Thank you in advance for your help.