Though zahavasdad is certainly incorrect, I am not sure ben levi is 100% correct either (where do you see that its the “same boat”?).
At issue here is the averah of chanifa (often translated as flattery) which coincidentally, has its source in this weeks parsha.
A classic example is the gemarah where chachamim told king agripas not to be sad (when he read the part in the torah that prohibited him from being king) and they responded “dont worry , you are our brother”. the gemarah says they were chayiv bnofsho.
Bottom line, chanifa is the implication to an ovrey averah that his actions are supported by you, or ok with the torah. It is an averah that some hold is yaharog v’al yavor (see rabeinu yona sharei tshuva) but even though we don’t pasken like that, rav moshe calls it a form of kefira (igros moshe orech chaim 2 #51)
so going to a gay parade or bar to be supportive of gays post orlando (as the OO did) is at the very least an aveirah and considered a form of kfeira