Overall I agree with this comment. A determinist would take this position even further and argue that there is nothing left that we could be in control of - it is causes and effects and maybe some randomness all the way down. Even those things we think are our free choices.
Yes, that’s the ultimate argument against determinism. Either one actually sincerely believe in determinism and trying to convince someone else they are wrong about free-will are just displaying their inability to take their hypothesis to its full conclusion, or they are just trying to dispel their own doubts by bending other people opinions.