As with Congressional committee hearings and State of the Union addresses, any disruptors at the Inauguration would probably be provided all the passes and credentials they need by their Democrat-member-of-Congress enablers.
The venue for the Inauguration is normally outdoors, not indoors like committee hearings or the SOTU, both much smaller and more restrictive venues and far less popular occasions. I say “normally” because, i.e., Reagan’s 2nd Inauguration took place in the White House because it had become frigid in DC. All events were cancelled except the swearing in itself, which date/time is Constitutionally mandated.
There is absolutely no comparison between a committee hearing and an Inauguration. Inaugurations are massive events. Committee meetings are held in what is a large conference room. The comparison would be like comparing a Trump campaign rally to a Clinton campaign rally then multiplying out hundreds of times.
I can’t remember a disrupted SOTU, not to say it hasn’t happened, but the passes to those are very restricted because of the limited quarters, and usually go to spouses or someone else very important to the Member. They’re not inclined to waste their ticket on a disruptor, and any disruptor would be carried out in a New York minute.
The Park Service, as I understand it, has issued permits to opposition groups in other parts of DC, away from the official events. That isn’t to say some agitators won’t come to the Mall or other venue sites, but they will be hard pressed to gain entry anywhere near the POTUS. If they do they may regret it when they encounter Trump supporters en masse.