I'm going to explain why we say he shouldn't receive communion.
We believe through the power of transubstantiation the when the priest quotes scripture and says the words "This is my body, which will be given up for you, take it and eat it" and "The is my blood, the blood of the new and everlasting covenant, take it and drink it" that these words are literal and Jesus becomes present in the bread and the wine. It's our most holy sacrament. If other Christians don't believe that's fine, but we Catholics do.
So we believe that you must be pure to receive the Eucharist. You can't be in a state of sin. If you are, then you mustn't take it. Because you are defiling and insulting Jesus himself.
So someone advocating easing up abortion laws if definitely someone that shouldn't be participating in our holiest of sacraments until he repents and stops this madness.