There is no evidence needed. Biden's decision to not supply Ukraine with planes and tanks is based on Critical Thinking - i.e., objective analysis and evaluation of an issue in order to form sound judgment.
There are no "hobgoblins" here - that's a silly argument.
Putin is desperate to regain control of Ukraine. Desperate people do desperate things. If we supplied Ukraine with offensive weapons, Putin would be justified to retaliate. However, if we just supply Ukraine with defensive weapons, (e.g., STINGERS, Javelins), then Putin has no grounds to retaliate.
What is "silly" is that you keep repeating an assertion that is unsupported by a thimble of empirical evidence, apparently believing that if you say it enough times it will become a stronger claim.
Sorry friend, that dog won't hunt.
Once more, please show us the "objective analysis" and the "evaluation" that demonstrates Joe made a sound judgement?
And, BTW, telling us that Putin is desperate, and sometimes desperate people do desperate things does not show us whether or not he would launch WIII with or without the arrival of so-called "offensive weapons". All your saying is that you've somehow read Putin's mind that he is desperate, and you somehow also know that means he won't launch WWIII if we keep doing the same as now, but will launch WWIII if we do even a little more.
So how do you know that? You don't. You don't even know if Putin even recognizes the arbitrary Biden-esque distinction between defensive and offensive weapons. In fact the administration itself has been unable to define it.
Your problem appears to be your inability to grasp that Putin isn't concerned with escalation, he is concerned with winning. If he can't win in any circumstance he will continue to escalate this war as far as necessary to win. He will bring in more troops, he will switch to leveling cities with bombers (as he did at Gronzy and Allepo), he will massively use theromobarics, he will bomb NATO supplied convoys, and if all that does not work, he will use chemicals.
The only thing he is very unlikely to do, is use nuclear bombs and launch WWIII because he still believes that NATO would do that to Russia.
"Not winning" or outright "losing" is what triggers Putin, not this childish abstract nonsense over "defensive" and "offensive" instruments of death.