Rashi in Bereishis 1:26 mentions the Pasuk in Melachim that refers to right and left of Hashem. Rashi continues, Is there a right and left of Hashem? Only it means those saying merits, which is referred to as 'right', and those condemning, referred to as 'left'. This clearly shows Rashi not accepting corporeality.
As for the Rashi in question, it is more than just a metaphor. Hashem reached out and struck them Himself. That is His hand. It wasn't meant to take on another meaning. The word Yad is to be translated as 'hand', not as 'assistance'.
Rashi is not addressing here the general approach regarding physical sounding attributes.
We should understand that the Rambam made a big campaign about this issue because it came to a head in his day. People became exposed to philosophy and understood for the first time concepts of the metaphysical. To these people, the Torah — which seemed to promote corporeality appeared outdated and narrow. Others rejected this and decided to take on the simplistic, face-value understanding.
Since the Rambam made this into a big campaign he devoted much of his Moreh Nevuchim explaining each reference that could have been taken to show corporeality. Any physical sounding term became taboo.
However, although Chazal and Rashi certainly didn't promote corporeality, they didn't shy from using descriptive terminology when it fit. It was understood that it is not meant to be taken in the physical sense, and we get past that. Today,we are pretty much back at that point. We don't have to explain that it is only a metaphor every time we mention Hashem listening to our prayer, getting angry, or proud.