"this action is arbitrarily discriminatory" - if so, this action is permitted. While there often are restrictions on
specific, enumerated types of discrimination (e.g. religion, ethnicity, gender, etc - though almost universally they apply to discrimination of people, not companies), those are exceptions to the general principle of "freedom of association" where people and companies are free to arbitrarily decide with whom they want to do business and whom they want to exclude - as far as they don't violate some of the specific restrictions listed in law. If a supplier does not want to sell to your company for an arbitrary reason, it's their right to do so.
"constitutes inflicting serious damage on another company without a legal basis" - again, that does not indicate any wrongdoing. Inflicting serious damage on another company is, by default, permitted (matching the core principle of "everything which is not forbidden is allowed") and is regularly done in the course of normal competition, winning over some other company in bids, recruiting key employees by offering them lots of money, targeting their customers with specific discounts, etc, etc.
If you're inflicting serious damage on another company, then both the intent and result is by itself legal, the only question is about the means. If you're inflicting serious damage on another company by legally prohibited means (e.g. theft or arson or illegal access to computer systems) or violating some established legal duty (e.g. "duty of care" as required by law in various service relationships), then the other company would be entitled compensation. But in the absence of that, if there's no specific legal prohibition to your action (for example, laws on anti-competitive actions tend to impose various restrictions), if your action is legally permitted, then if some company suffers because of that, it's not your problem. There are restrictions on what actions are legally permitted (law on tortious interference might apply here, and if there's some fraud, injurious falsehood etc then it matters) but if they do have the right to arbitrarily end the contract, then that's it, they are not responsible for the damages.