Trademarks aren't explicitly protected by the Constitution. Article I, Section 8, Clause 8 grants Congress the power "To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries" (i.e., the power to issue copyrights and patents, which are distinct from trademarks).
Federal trademark protections are derived from the
Lanham Act, which requires "likel[ihood] to cause mistake, or to cause confusion, or to deceive" as the standard of evidence for trademark violation. It's a stretch to say that someone attending a Backcountry Babes avalanche safety course (a service Backcountry.com doesn't offer) or purchasing an electric bike (a product Backcountry.com doesn't offer) from Backcountry eBikes would likely be deceived by the names of those entities into thinking they were actually shopping at Backcountry.com. It's not like Backcountry.com is going after some upstart outdoor gear retailer using back-country.com as their sales website and using a right-facing instead of left-facing goat logo. These are indiscriminate, frivolous suits based simply on use (with no intent to deceive) of a commonly used term that has been around since
250 years before the founding of Backcountry.com.