Countries are defined by their borders, and governments are perfectly justified in using force to control access to their territory. The fact that there is a pathological unwillingness in some industries to comply with immigration law (in collaboration with some politicians and administrators) and a willingness to externalise the costs of their "cheap" labor might have given you the impression that this state of affairs was inevitable or necessary, but it is just a mechanism for corrupt businessmen and opportunistic politicians to gain monetary and political advantage at the expense of citizens, as well as technological progress (an endless supply of unskilled and semi-skilled labor below the market rate removes the incentive to invest and innovate). Factors like birthright citizenship and chain migration further exacerbate these problems.

Crypto deals with digital transactions. There's essentially no geographically relevant scarcity.

Migration impacts all kinds of things which are intertwined with physical scarcities and order- community service funding, housing needs and so forth. Having an orderly process for migration isn't at all related to cryptocurrency; many aren't actually private at all, and for the most part merely allow control over the supply to not be controlled by a central agency like the federal reserve.

Being opposed to unlawful migration would be the equivalent of opposing people generating coins off the chain then forcing them in, creating more than were actually generated by mining. (I may have butchered the analogy, hopefully it at least makes some sense as to why they may not see it as an ironic or hypocritical stance).