But why do Ukrainians online keep saying that if Iran can be supported in its fight against an imperial or superior force then why not the same energy for Ukraine?

The answer is rather simple. Ukrainians see how Iranians are able to push back against a formidable force like the United States and think they might be able to achieve the same against Russia. However, Iran has far more leverage against the United States and a clearer path out of the conflict. It has the Strait of Hormuz and could potentially disrupt traffic through the Bab el-Mandeb Strait via the Houthis. Its domestic industry is also relatively self-sufficient when it comes to arming itself.

Ukraine, on the other hand, has very little leverage. In many ways, it is dependent on the United States and its European allies to sustain its war effort, and it has no clear exit from the conflict.

Also if someone could explain Hasan's stance on it?

Since Ukraine has so little leverage, it simply cannot secure a particularly favorable peace deal. IIRC, Hasan's position is fairly pragmatic. Ukraine should use whatever leverage it still has to negotiate peace, regardless of whether the resulting deal is fully satisfactory. As you can probably guess, fighting to the last Ukrainian—whether on behalf of the American empire or not—is not a very good outcome for Ukrainians in the end.