I have to wonder about the existence of this too, especially since you used a plural. I can not think of any group of non-Tesla owning fans of other brands that were here making "backhanded comments about Tesla". It is not like this place is attracting droves of BMW fans, for example.
Tesla is a new brand, it is obvious most people have a lot more of experience in other brands - even fandom, that is to be expected. But I genuinely can't think of many that fits
@stopcrazypp's description. Most of what I see people in this thread pointing out as "negativity" come from actual Tesla owners who have had negative experiences with Tesla.
Having said that, I've found most automotive forums overall being very allowing of other brands. They often even have named sub-forums for them. People tend to move from car brand to another much more than they perhaps do in some other things in life and they are long purchases, so forums tend to wish to hold onto their members even if they take a three-year stint with the competition.