All in all, a decent article. That being said, there are a few points I'd like to expand on and talk about (in the order the appear in the post).

"Groups like ANTIFA"
While I don't think you think the following, many do - quite often people with think of antifa as this one, big, monolithic group. This lack of understanding that people have is quite issuesome. Instead of seeing a great number of fairly independent groups which are all anti-fascistic and often work together, but aren't actually the same, people quite often see "antifa" as a single group. In doing so, it's easy to condemn all of "antifa" because if one member or group does something wrong it can be blamed on all of "antifa" (for whatever reason; US anti-fascist groups are quite often quite new and while being well-meaning they can still mess up). Instead, I typically use the term "anti-fascist groups" because most people are generally against fascism and it makes people stop seeing us as one big group, minimising the ability of a single poor decision discrediting all anti-fascist groups. Furthermore, by using these same tactics it's easy to frame groups because we tend to hide our identities, at least while protesting.

(I don't think you actually think that it's one big group, I think it was just an imperfect choice of wording)

"The Nazi's were elected"
Saying this seems to imply that they were peaceful and democratic to gain power, which is a common misconception. At first, they planned a violent uprising. They did this, referred to as the Munich Putsch, but it failed. Hitler was imprisoned (where he wrote Mein Kampf) - he was released really quickly because those in the judiciary system on his case were sympathetic.

After this, the Nazis changed their strategy. While still utilising violence (e.g. they sent people to break up Communist meetings - the Communists being their main opponents in terms of "radical" politics [I guess the Nazis were radical, just in the wrong direction]).

When the election came, people turned to either the Nazis or the Communists. The Nazis got the greatest amount of votes, but lacked a majority - an issue particularly in the Weimar political system. This resulted in the requirement of a political deal, which the Nazis had tried in an election however many months before that but Hindenburg, Papen & co. refused. This time they didn't, making Hitler vice Chancellor. They thought they could control him, but of course they didn't.

From there it was just moving up the ladder; he becomes Chancellor and soon Fuhrer by manipulating article 48 of the Weimar Constitution. All of this is done with illegal and violent methods at parts, he just found that in the democracy of the Weimar Republic, democratically worked best with the help of the Sturmabteilung (the "Brownshirts") and other parties. He also killed off a load of political opponents and the military in events such as the Night of the Long Knives and others.

So from this, you can see that a lot of their tactics were illegitimate or at least slightly bending the rules, not just the acts they passed.

Black bloc tactics
Expanding on the black bloc tactics, it's used both offensively and defensively. Quite often they'll do both; provide physical defence for allies and go on the offensive when required. It's to do with what you said, one of unity and avoiding arrest, but they have also evolved into a quite effective tactic with violent characteristics in certain situations. There's obviously a lot more that can be written about this, but there already has been elsewhere.

Overall Thoughts on Antifa
Anti-fascist organisations and groups are great. In America they're still pretty new in comparison to ones elsewhere, so they've messed up in places and will mess up again, but all in all they positively contribute quite a lot. That being said, I feel a lot of their tactics, while seeming obvious to the more radical of us, will seem as random violence by most, or at least many, people. To avoid this, we could possibly do more to explain to people the reasons why it's done. That is of course made easy with the internet, which is frequently used, but we should also be looking for mediums with greater audiences, such as mainstream television if possible.

Again, decent post - worth the read. This isn't really arguing against much said in the post, just a few developments on what you said really and a bit of my own views on Antifa.