a taboo implies that the discussion is avoided "just because". I've already pointed out why discussing bans at this stage is a bad idea, but since we're also bringing map selection into the discussion, let's go over that too.
map selection at this stage is out of five maps.
yes, the game will eventually have 12+.
yes, we can expect people to want to refine these maps down to a smaller selection.
yes, we will have this discussion at some point. but these maps won't even be out for months. removing one out of the five maps at this early stage is patently ridiculous.
people are adamant because there's absolutely no reason to even bring bans (or even map selections) into the discussion. with no benefit and the risks as I've already stated (mainly concerned about the "just ban it" mentality that these discussions breed), it's not a taboo, it's justified.
But just because a map is adequately sized for 4v4 doesn't mean it is automatically built for competitive. In halo 3 for example, maps like epitaph, cold storage, high ground, ghost town, are all 4v4 sized maps but they were never used in competitive because of other reasons, their map design was well suited to competitive.
these maps would be removed from the map pool after extensive post-release analysis, which is the point I was making. in splatoon's case, the fact that there are only five maps (for now) means that the only way a map gets removed from the map pool is if it's so incredibly awful that it must be removed. symmetrical maps tend not to have this problem.
and while I don't remember the other three maps, cold storage was removed from the map pool for being a small FFA/1v1 map that was obviously not going to work with the competitive gametypes.