The law is fairly clear on these matters. Reasonable force is permitted in self-defence, and that includes killing your assailant in some circumstances. But it isn't unreasonable to investigate all the same. A man has died. Burglar he may have been, but stealing hasn't been a capital offence in this country for a very long time.
It's not a matter of having sympathy for the dead man, either. I have none for him. But if he was killed without lawful cause -- ie, murdered -- then a crime would still have been committed.
As it happens I doubt he will be charged and, based on the account in the article he won't be -- but not to investigate deaths of (suspected) criminals under any circumstances would be tantamount to legalising vigilante justice.
Meanwhile, spath is just a wind-up merchant. Ignore their posts.