Like I said, base your argument on in-game evidence and not lack thereof.
Otherwise you have no proof to your claim.
That's a Nirvana fallacy. You're limiting evidence to one kind of possible outcome. If it's not directly stated in game, it can't be true. No other evidence can be accepted when presented.
Does it have to be directly stated in game? He's a scientist. He keeps a piece of a Reaper in his lab. He's had it within his possession for the last 2+ years. He's fascinated by Reapers and Leviathan. He was not indoctrinated (nor were any of his staff, at least not by the Reaper Artifact). He took appropriate measures to ensure the fragment could not indoctrinate anyone. He had himself and his daughter (and others possibly in his staff) take part in psychiatric evaluations at regular intervals to make sure he wasn't being indoctrinated. Inductive reasoning tells me that all of this is supporting the claim that he did indeed study the Reaper fragment. And he was not indoctrinated because he took proper precautions when studying the Reaper fragment. This tells me that you can indeed have proper precautionary measures to minimize, if not completely negate, the threat of Reaper indoctrination. That, in essence, is my argument.
Your argument is that because it is never directly stated that he studied the Reaper fragment, my claim can't possibly be true. You provided no evidence to prove your own argument. You've changed the argument, and dismissed my evidence by moving goalposts to explain how mine isn't correct, while holding your own claim as likely (without evidence.)
Make an argument. Don't attack mine, deconstruct it. If you can, I'll concede. If you can't, then I've won the argument. Stop shifting the burden of proof back on to me. I've given my evidence. Give me yours.