It is amusing you censored your own words when you claim they are nothing to worry about !
How do words become rude ? Merely by their usage. Take a word like “nigger” or “wog” – these were regarded as acceptable descriptions of black people as recently as the latter twentieth century but now are regarded as terribly offensive. This is because they came to be used in derogatory ways and to imply very negative things. Contrast with the word “queer” which was at the same time a term of insult towards homosexuals and has now been co-opted by the gay community and might be used as a positive expression of a lifestyle.
To say “but they are just words” is to rampantly ignore the power words can have. One can go on TV and use only words and spark race riots in minutes – words are never to be underestimated. Similarly one can use words that are not particularly nasty but by intonation and juxtaposition make you feel very uncomfortable.
The etymology of the two words you cite is difficult to establish, partly because a word such as fuck was considered too rude to write down and thus was excluded from early editions of the Oxford English Dictionary. The OED offers a comparison to thirteenth century usage of a word fuken but is clear that the ultimate derivation of the word is unknown. It would not surprise The Conduit if in one hundred years the word has lost its status as a bad word through over-usage.
The word cunt is probably retaining its severe meaning (which also dates back to the same period). It is possible that these words gained their status as they were words used by the common folk in bawdy conversation and as such were regarded as particularly coarse.
The Conduit‘s belief is that it should not be necessary to censor such words other than for each person to ask themselves whether the usage of the word in any given context is justified, bearing in mind the meaning that one wishes to get across and the efficacy of the chosen words for the audience. One doubts that hearing your vicar say “Let us fucking pray” would strike the right note.