There are Neo-Nazis in this world. They scare me & I would not want to downplay the pockets of Nazis in the US, Germany, or elsewhere. It's hard to see how a gesture of blessing can be seen as creeping Nazism.

For comparison, I'm Episcopalian; when several priests are con-celebrating communion, the ones off the the side will extend thier arms straight out, palms down, probably a little lower than the Nazi salute, as part of their participation in the rite. The farther away one is, the higher the arm will usually be.

The physical attitude of entending a blessing on an individual is to extend the hand over the person's head. If the recipient is standing, or those extending are far away, the natural way to do it would be in this gesture that looks to you like a Nazi salute. How might you symbolically but physically extend this blessing?

In addition to what everyone else has said, there is not only a hand & arm position involved, but a gesture as well. To my mind the Nazi salute should include a 'coming to attention' sort of gesture. It is not just the arm position, but the entire body. You've admitted that not all have straight arms. What's their body language saying? If the arms are all raised at different times, in individually unique body attitudes, you don't really have a salute of any kind going on.