I believe it could be left out and keep the general meaning. To my ear*, Это kind of reinforces the "identity" aspect, in the sense that that you're sort saying "I am indeed that exact person" or "I and he are synonymous".
Make no mistake, it's a very weird sentence, and my sense is that it is only at home in literature or drama.
- Born in the US to native Russian-speaker parents.
It should certainly be accepted, seeing that many of us have been programmed by teachers or parents to produce and accept this or similar phrases, such as 'It is I / he / she." However, is there anyone among us, who, when pointing to himself or herself in a photo, would actually say: This (person) is I! ????
As a native US English speaker, I use pronouns in the nominative case after the verb of being in some instances more than others. For example:
1) The phone rings. John picks it up and says, "Hello"? The caller asks, "May I speak with John Doe"? John answers, "This is HE. But, really you should speak with Judy. It is SHE who knows all the answers."
2) Hey! Is that the guy? Oh yeah! That's HIM!
The first example follows the rule, while the second does not. Both are commonly heard. Like most languages, English grammar is consistently inconsistent. But, first learn and use the rules, then the exceptions... not the other way around Besides, compared to Russian, learning English declensions is a breeze!
If you wish to delve deeper into controversies and history about the use of pronouns by Americans, wikisource has The American Language/Chapter 41 (H. L. Mencken) on line.
It would be much easier for English speakers if Russian regularly used a word for 'to be' ("Я есть Грут!" &c.), rather than just a dash/pause or nothing at all! Think of это here as being 'this is' rather than just 'this' - you can then neaten up 'I - this is he/him' to 'I am he/him' without so much trouble. There are Russian words you could use, but you will sound ridiculously formal https://forum.wordreference.com/threads/using-the-verb-%D0%AF%D0%B2%D0%BB%D0%B0%D1%82%D1%8C%D1%81%D1%8F.2392865/ - much the same tone as using 'I am he' rather than 'I am him' : p.
I can't really get my mind around why here are mostly comments of whether or not "I am him" is the correct form in English and not whether or not "Я это он" is correct in Russian. You can't translate 1:1 the languages, you have to adjust the sentence a bit more. If there is ever situation that you would need to use this confirmation form in Russian, you would rather use "Я он" and leave the "это" part out.
That would be 'Это я'. The sentence given is for saying you are a particular man, or at least a masculine noun.
Maybe you and a friend are playing Monopoly and are using the dog (собака) and boot (ботинок) pieces. You could point at the boot and say "I am he/him" because the boot is masculine, but "Я это она" for the dog, which is feminine because of ending in 'a'.