It is actually quite clear…But I’m not sure if I can clearly explain it
The OP’s scenario has nothing to do with Abortion so let’s dispose of that one first.
Abortion is wrong because it is murder. The death of an innocent human being. For this reason, the fight to educate and to end abortion is a civil as well as a religious moral good. The matter being discussed here is different. The damaging of condoms in the store has no effect on abortion - or - if it does it would be to increase abortions as those using the damaged condoms abort the resulting pregnancies…
Now to deal more precisely with the scenario…
The action proposed in the OP is morally wrong because it violates the Law of Love…Love your neighbor as yourself. It causes damage to your neighbor in a couple of ways.
For the store owner, it results in returns, complaints, lost business and revenues.
For the user, it could cause them to spread disease or a pregnancy that would then…
Cause harm to the child so conceived because the Child would most likely be aborted.
The scenario also violates the Law of Love by circumventing the person’s free will choice to NOT be Catholic and to act on his conscience - using a method of contraception that - in point of fact - prevents conception - as opposed to aborting the conceived child as so many other, chemical, methods do.
As an adjunct to this violation of the law of Love in this way, once it is known that the condoms were deliberately damaged, it will cause the user, and many others to “blame” those “evil pro-life Christians” and make harder the task of evangelization and persuasion that Abortion is wrong in all it’s forms.
I hope this helps you understand better.