Red cross heals people, military kills people.

Well, one just helps the civilians, the other helps with military superiority. Now the big question is, is using of weapons on aggressor something you are OK with or not? Many people are not, so its perfectly fine to help like that. It might not be directly used for killing, many barely 18 years old drafted Russian soldiers are vastly demoralized and surrendering. Having superiority helps to achieve that.

That being said, I come from eastern Europe and whats happening is seen in eastern Europe as existential fight also for us down the line. Could be compared to how ie US felt during WWII with Hitler and axis. Hundreds/thousands of men are volunteering in each state to go fight in this war. These are not Ukrainians in any way, more like patriots for lack of better term.

Personally, I've donated to the org directly in Kyiv which might use it for aid or for weapons, both are good with me. I would say I hope for peace, but Putin doesn't want it at all regardless of bloodshed, so let's not be naive and kick his ass instead.