Why?
If +Fellay never spoke like +Tissier (which is basically giving +Fellay the benefit of the doubt) then we have an even bigger problem.
The example quote from +Tissier was very +ABL and +Williamson-like -- very classic SSPX. In a worst-case scenario, if we can't produce quotes showing +Fellay was once Traditional as well -- we don't need to throw out the argument, thread, etc. we just need to conclude that +Fellay was never Traditional! Or else what is this, "shoot the messenger"?
I fail to see the problem you have with the OP. The argumentation is strong either way, with or without 10-year-ago Trad +Fellay quotes. The argument is anything but weak.
Why would it be difficult to find a quote from +Fellay along the lines of what +Tissier said. Maybe +Fellay was softer than the other ones out of the gate? I don't know. But the contradiction is based on the unproven (in this article at least) that +Fellay thought exactly the same way. +Tissier and +Williamson have always been a little more hard-line than +Fellay and +Galaretta.
If this is true, there should be no shortage of +Fellay quotes from which they could make the same case.
Major: +Tissier used to be a hard-liner.
Minor: +Fellay used to speak like +Tissier.
Conclusion: +Fellay used to be a hard-liner.
Minor is gratuitously asserted but not proven. I don't understand why you don't see the logical flaw with this reasoning. Do I have a hard-time believing that +Fellay used to be a hard-liner but changed? Of course not, but I would like to see this established with real evidence.
But the other alternative is that +Fellay was soft (relative to +Tissier) even in the beginning, and perhaps even that he was an infiltrator put into the SSPX to bring it down.
After all, it's well known that he wasn't on Archbishop Lefebvre's original list of priests to consecrate ... until some outside pressure was brought to bear,