Even if that's true, what right do the Police have to decide that he's not allowed to try and save his own son (or stepson), even if it means he may end up dying in the process?
Put yourself in his position - how would you feel if it were your son/daughter and some police officer physically prevented you from trying to save him/her? On what possible authority do they rest to make such a decision, that he should not legally be allowed to enter the home?
Now, assuming these are the facts:
1) House was on fire
2) Father/Stepfather wanted to try and rescue son/stepson
3) Police physically prevented him from doing so
then this is complete ( profanity deleted by Moderator ). It doesn't matter if it's irrational, the father was only putting himself at risk.