A couple of things...
1) No team has won an NBA title as lower than a 3 seed in over 20 years (Houston as a 6 seed in 1995, it was 1969 before that with Boston as a 4 seed). So that means that in any given year, there are 6, maybe 8, teams with any real shot at the title...leaving 22-24 teams who we pretty much know won't win it. A third of the teams in the NBA are going to miss the playoffs (including the play-in games) altogether. The worst thing you can be in the NBA is a team not good enough to win anything of note but not bad enough to really benefit by getting a high draft pick. So, if you're not going to be a top 3-4 seed in your conference, not a playoff team on the upswing with good young talent or, especially, if you're not good enough to make the playoffs, you should be trying as hard as you can to be as bad as possible so that you have the best chance to get a draft pick that leads you to a top-tier talent. In essence, if you can't be very good or better, you should be bad with a purpose. Top-tier talent is pretty much the only way to win anything of significance in the NBA and, if you don't have it, you should be doing everything you can to acquire it.
2) Small market teams, in particular, need to utilize the Draft and, therefore, tanking as a means of talent acquisition. For the most part, small market teams struggle to not only acquire talent (without massively overpaying for it), but to retain talent once they've acquired it. The surest way they can acquire talent is to draft it. If small market teams in the NBA (especially those without outlier talent draws like Miami) are to ever be anything other than cannon fodder for the bigger & (largely) better teams, then they have to be able to maximize their talent acquisition opportunities through the Draft and that essentially requires tanking. Again, if you're going to be bad, you should be bad with a purpose and do everything within your abilities to be as bad as possible so that you maximize your chances to acquire the top picks and, hopefully, the best talent coming into the league. (IMHO, if the NBA moves any further into anti-tanking territory, they might as well just cut/move a handful of small market teams because they are very unlikely to have any real consistent shot at talent acquisition.)
So, those are the reasons that I am pro-tanking in general and, specifically, for teams that are outside the playoffs and need additional talent.
In essence, IMHO, this ultimately comes down to one's opinion on a different question...is the NBA primarily a sports league or an entertainment company? If it's a sports league, then teams ought to be doing everything they do with the goal of acquiring the best talent possible, including being as bad as possible unless you're among the top teams with a real chance to compete or already on the upswing with suitable talent to get there. If the NBA is primarily an entertainment league, then the NBA should want to prevent truly bad teams in order to raise the nightly entertainment value of each game and therefore should be anti-tanking. If it's not obvious, I would prefer the NBA to primarily be a sports league and therefore I am pro-tanking.