It is possible to insult fascists without being ableist or fatphobic. A physical feature does not equal values, behaviour, or intent.
All you’re doing when you make fun of fascists’ bodies in your meme is tell your peers that you hate anyone who might share some of those physical qualities.
Those fascists don’t even see your meme and will likely never see your meme. Your audience is your fellow social media users.
If your insult could apply to non-fascists then it’s not an effective insult anyway. People will act violently no matter what they look like.