Gender in grammar is just another dimension to word, like case, number or tense. It isn't even necessarily masculine or feminine. German has a neuter gender as well; Arabic has a two level gender system with masculine/feminine and animate/inanimate. Dravidian languages have genders that distinguish a noun between human and non-human classifications.

Grammatical gender largely serves to distinguish the antecedents of pronouns in the same sentence through agreement with other words. It isn't necessary for a language to function(only 25% or so of languages have it), but adds granularity with fewer words.

The reason people who gender a particular noun masculine in one language are put off by them being gendered grammatically feminine in another isn't because of bias for or against one sex, but the normal jarring effect of differences in syntax. Some languages have different rules for apposition that mess with you, and some languages have different rules for whether an adjective for a noun follows or precedes the noun to which it applies, or whether there's agreement in number or not.

English is a particular one of confusion for non native speakers because it's a Germanic language with a simplified Germanic grammar structure(absent grammatical gender and noun declension) but has tons of French loanwords and cognates that brings with them French syntaxes and orthographies(German doesn't have silent letters for example)