Spencer would never beat Mera, even when he was particularly noisy or obnoxious. When his face was swollen, Spencer won't look at him straight in the eye.

At first I thought it was because I have a soft spot for Mera, so Spencer respect my choice.

Later when Ha and Max appeared, Spencer treats them with disdain.

So I guess Spencer likes Mera. They have been friends for 7 years.