When the Torah is talking about the "ger," pshat is CLEARLY referencing an immigrant.

Clearly Avraham was not a convert when he was a ger with Bnei Chet.

Clearly the Jewish people were not converts when they were geirim in Egypt.

And more.

Rashi agrees on Exodus 22:20 agrees:

כָּל לְשׁוֹן גֵּר אָדָם שֶׁלֹּא נוֹלַד בְּאוֹתָהּ מְדִינָה, אֶלָּא בָּא מִמְּדִינָה אַחֶרֶת לָגוּר שָׁם:

Wherever the Torah uses the word 'ger,' it refers to a person who was not born in that land, but rather comes from some other land to live there.

The Chafetz Chayim in his Sefer Hamitzvot (61) agrees:

סא. מצות עשה לאהוב את הגר. שנאמר: "ואהבתם את הגר" (דברים י, יט). וזוהי מצוה נוספת על ואהבת לרעך כמוך (שהרי הגר הוא גם כן בכלל ישראל). והקב"ה אוהב את הגר דכתיב "ואוהב גר לתת לו לחם ושמלה" (דברים י, יח), ונאמר "ואתם ידעתם את נפש הגר" (שמות כג, ט), ופירוש גר כאן, הוא שבא מארץ אחרת ומעיר אחרת לגור אתנו, ומכל שכן גר שנתגייר.

It is a positive commandment to love the stranger, as it says “And you shall love the stranger” Deuteronomy (1:19). And this is an additional commandment on the commandment to love your neighbor as yourself, for a ger (convert) is included in Israel. And God loves the stranger, as it says “[God] loves the stranger to provide bread and clothing” (Deuteronomy 10:18). And it says “And you know the soul of the stranger” (Exodus 23:9). And the meaning of a stranger here is one who comes from far away land and a different city to live with us, and how much the more so one who converts.

Rav Hirsch agrees:

“...the great, oft-repeated in the Torah, basic law is laid down, that it is not race, not descent, not birth or country or property, altogether nothing external or due to chance, but simply and purely the inner spiritual and moral worth of a human being, which gives him all the rights of a man and of a citizen. This basic principle is further ensured against neglect by the additional motive for you were strangers in the land of Egypt. Here it says simply and absolutely for you were strangers in the land of Egypt, your whole misfortune in Egypt was that you were 'foreigners,' 'aliens' there. As such, according to the views of other nations, you had no RIGHT to be there, had no claim to rights of settlement, home or property. Accordingly, you had no equal rights in appeal against unfair or unjust treatment. As aliens you were without any rights in Egypt, out of that grew all your slavery and wretchedness. Therefore beware, so runs the warning, from making rights in your own State conditional on anything other than on that simple humanity which every human being as such bears within him. With any limitation of these human rights the gate is opened to the whole horror of Egyptian mishandling of human beings.

We could go on and on...

In terms of a strictly halachik obligation, it gets narrowed in the Bavli to focus on strangers in our midst in an exilic world, aka converts. But the value is still there and as we've seen, many argue that even from a strict halachik perspective the mitzvah applies to immigrants.

It is not "liberal politics masquerading as Judaism" when Jews try and protect vulnerable immigrants in society. It is a deep expression of a fundamental Torah value. And it's needed now more than ever.

haggadah Section: -- Cup #2 & Dayenu