I would like to start this off by saying that I know T has the potential to have harmful effects but I know it a lot less likely then many believe

So, in summary, I just re-came out to my parents. I went fairly well. Way better than the first time. But the kept saying that they're worried transitioning will physically hurt me. Does anyone know any research that I can offer that debunks myths or talks about the scaremongering in the realm of transition. Please and thank you

Honestly, they can look at the men around them.  Are any of them being harmed by it? 

It'll just hormonally change you into a teenage boy.  Of course, since you're female-bodied, it'll change some other parts, like bottom growth will happen, but otherwise, you'll look and more than likely sound like a teen boy until your body has finished changing.  Once that's done, you'll simply look like any other man in your family. 

Its all really just common sense once they calm down and think about it.  Just in case they're still worried, I found this doing a quick google search.

https://en.wikipedia.org/wiki/Transgender_hormone_therapy_(female-to-male)

Ryuichi

Modern treatment involve starting at a low dose then ramping it up to a transition dosage. Blood test are run before your first dose and at regular intervals after that in order to catch any problems early. Problems are rare but should they appear, they will be addressed before they become dangerous.

That said, I have been nosing around in my past and located the FTM advisor that was in my therapy group. He probable started T in his early 20's and he is now over 70 but still alive and enjoying life. Self medicating can be dangerous but under proper medical treatment you can expect a long life.

Best way if you can't convince them would be to get a doctor to explain it to them. The only risks associated with T that is generally recognized is the increased risk of heart disease/stroke/clots but no more than any normal man experiences due to increased blood cell count. Polycythemia can be easy remedied by a trip to the blood bank, or just get it drawn at a surgery, and the risks can be practically mitigated by following a healthy lifestyle and not being overweight. If they don't believe you, then maybe they would a doctor if you got them to go to one with you and explain that.