"You're totally missing my point,"

Not at all. Your point was "we dunno"

"...which is that we don't know one way or the other. At this point, it's conjecture, and to try to state that as scientific fact is detrimental to science."

Human beings are smart enough to work on fractal facts. We can make educated guesses based on what we do know. Conjecture and science go hand in hand. Theories require an original hypothesis before any evidence is even gathered. The odds of me being right are frankly higher than my being wrong. The consequences of my being right demand that we take such possibilities seriously.

"No one except you is jumping to the conclusions you are."

Absence of evidence is not evidence of absence. Most scientists agree that we are not alone. Asimov was quoted as saying "wimps don't become Top Dog".

"We don't fully understand the pre-conditions for Earth's life, and we can't recreate them."

Amino acids have been created in laboratory tanks. The whole Earth was once laboratory tank! Life was inevitable. It appeared almost immediately.

"Until the application of the scientific method, any idea is a conjecture or theory."

Science has its flaws. It is not perfect. Some things must be analysed in relation to what we know and educated guesses made. Most scientists now believe life in this universe to exist.

"so age doesn't necessarily have anything to do with advancement."

Age is a factor. We are talking about billions of worlds. Averages must be employed. Its commonsense that more advanced life than ours must exist if we are not alone in this universe.

"Inter-species conflict isn't the only evolutionary factor."

Its the main one. Others are environmental challenges.

"We know nothing of other species' social psychology (if they do exist). Conjecture."

Again parallel evolution tells us otherwise. Even if only one percent of spacefarers were aggressive they would overwhelm and destroy the 99% who are pacifists. Ofcourse its more likely to be 99% being dangerous carnivorous survivor types like us.