Well, the concern he has voiced is a legitimate one, and I haven't seen his points rebuffed in your post.
So, Kalou for sure isn't positive, because he only got the results of his testing back before the incident. We know that for a fact, because Hertha said it in their statement.
We also know that Hertha's players are training in four groups of eight, so it's not like they don't have contact beside the handshake incident. Which kind of makes the incident unimportant, as there are way more dangerous types of contact around the training ground than the handshake itself.
Handshake is much less of a risk than training together and especially playing games. So, if we are looking at the unnecessary behaviors, it's hard to understand why the handshake is such a problematic thing, but football itself isn't.
To me it looks like that Kalou actually played well into the books of decision makers, as they had the chance to swiftly remove someone who is not following the rules, and picture themselves as if they were on the top of the situation. Only time will tell if they are, but it does look like a hypocrisy to punish someone for handshake while at the same time encouraging players to engage in way more dangerous activities.
As far as I know, Germany still has over thousand new cases daily, I really think the kick-off is too sudden. South Korea has practically eliminated virus, and I'd say they should be viewed as golden standard in terms of how to run the society in pandemic. Haven't even had the lockdown, but have made absolutely sure that transmissions are close to zero before resuming the season.