First, the traditionalists, while growing steadily in numbers, are still a fairly small contingent among Catholics overall. They've had, in most cases, to fight with their bishops for everything that they've gotten, even the crumbs that they often have to settle for. Many, many local ordinaries have never been "generous," as the Indult urged, in supplying venues, priests, and permissions for other Sacraments to be given in the older Rite. This can lead to a certain pugnacious projection of appearance on the part of traditionalists. I don't say that that's a good thing; I am just saying that that is how human nature tends to work. Would that we were all saints bearing patiently with trials and adversity, but such is not the case. Such is often not the case among the mainstream, either, in their dealings with us. "Elitism" and smarmy condescension certainly cuts both ways!
Second, one needs to consider that, in the days of the Indult, when there was usually just one venue per diocese (among the ones granting the Indult at all, of course), the TLM at Saint So-and-So's might often attract some of the more..."colorful"... types in the diocese. This is only natural. At all times through Church history, there have always been a few unstable people in most any parish. Some of them have always manifested their instability via excessive pietism, rigorism, etc. Well, when there is only "one game in town" for people afflicted with some form of hyperpietism or whatever, reflected in a tenacious attachment to the TLM, they will naturally congregate in the one allowed venue out of proportion to the majority of more squared-away traditionalists. Here in Boston, we have always had a few folks a can or two short of a six-pack in the Traddie community. Sometimes, they say and do embarrassing things, and get press attention or diocesan attention way out of proportion to their actual numbers. At their peak, I would say the constituted no more than 15% of the Indult congregation. They're a much smaller proportion now. Certainly, there are many more than that among the sedes, but I'm not talking about them. I presume Mark Shea isn't either.
The vast majority of Traddies in the current Motu Proprio setup are quite stable, normal people, willing to get along perfectly calmly with their Novus Ordo fellow Catholics, and they aren't anywhere near the angry, ugly people Shea seems to imply are everywhere. And, again, there are more than a few Catholics in Novus Ordo parishes who are every bit as angry and ugly. They are not representative of the whole NO culture, either. Shea needs to get a better handle on both general human nature and how small populations within a larger culture largely ignorant of them, centered on (usually) one venue, tend to concentrate people with an "attitude."
As for all of the foregoing, now that the Motu Proprio is beginning to bear good fruit, and more venues are opening up for the TLM with a better "attitude" on the part of many bishops and priests (the result of a "talking-to" from Rome, perhaps, but a better, more open attitude, nonetheless), and a more mainstreaming capability is reached as overall numbers grow, we will see much of this "anger" disappear. In a couple more years, those Traddies who, up to now, have been disaffected over real and imagined slights will have either gone off the reservation to the sedes, or will have their concerns (finally) addressed and settle-in to life as the MP envisions it for them. A little respect and understanding from the majority can do wonders in fostering a little benignity among those who feel embattled!